Friends with Benefits – Part 3

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After my close call with my girlfriend I should have been more cautious but I wasn’t. I was addicted to having sex with the female dog. My new knot was working great and really added to my experience and pleasure. It seemed so natural now. I had my cock about halfway inside her vagina and was working it deeper. She seemed extra hot and tight today. I felt my swollen knot touch the lips of her vulva. It was time to push it inside her. She never resisted me and always cooperated with our mating. I felt her open up more and soon my knot popped inside and was well seated in her vagina.

I turned around on her and gave our connection a test tug. We were firmly tied. I relaxed and settled into cumming inside her. I started to think about what had happened over the last few months I was fucking my girlfriend less and less and her female dog more and more. It seemed like my cock just stayed inside her. I didn’t want to admit it but my cock had changed. It was always soaked in the fluids her body produced and the flesh of her vagina was in contact with the flesh of my cock constantly. I had absorbed some of her cells there was no doubt. I tried not to think about that because I know I wasn’t going to stop.

Probably the biggest change was how I orgasmed now. I couldn’t start cumming until my knot was fully seated inside her. Once my body knew we were tied and officially mating it would release my sperm involuntarily. A normal guy is done cumming in a couple of minutes. My orgasms would last 15-20 min. I always shot a huge load of sperm. I knew she wanted me to breed her and so that became my purpose.

I was really enjoying our mating that day. I could tell my cock had finished spurting so it was time to try and get it out. My knot was very big and always a challenge to go in and back out. S low steady pull until it was ready on its own. It took about 30 min but finally I felt a movement and slowly her vagina released me. She licked me a little and then walked off. As I sat there recovering I suddenly realized something. I couldn’t remember using the pump to move fluid into my knot to enlarge it. Yet when it was time to get it inside it was already swollen. And it got bigger once inside. Did that happen on it’s own?

I went back over step by step and now was convinced I didn’t use the pump at all. All the swelling had happened on its own. Was this another change my body has made? I actually kind of liked the idea that my know would function on its own. That was more natural then having to manually inflate it. I would have to test it tomorrow. I did realize that it might be a problem if I tried to have sex with my girlfriend. She would know for sure if I tried to fuck her and my knot started to swell on its own. I took a shower and then went to bed so I could avoid seeing my girlfriend.

I woke up the next morning feeling refreshed. My girlfriend had already left for work. I decided to do something routine. I put a t shirt and some boxers on and sat down at my computer. After awhile the dog came over and started sniffing around. I really wasn’t paying attention when I felt her lick my cock. It had been hanging out of the loose legs of my boxers. I shifted in y char and exposed more of my now hardening cock. The dog was now licking my cock from the tip down the fat shaft. The foreskin remained in place fully covering the glans. Lately it had become very tight and rarely retracted. Usually that only happened when I had it inside the dogs vagina and it was pressing into her cervix. Otherwise it stayed covered.

My cock was swelling so I just thought fuck it I know what she wants and so do I. I peeled the shirt off and stepped out of the boxers so I was naked. I got down on the carpet in the middle of the den. We had done this maybe a hundred times so she knew what the routine was. I knelt and she backed up exposing her labia. She was wet and so was I. A strong odor of sex filled the room. I took my cock and pressed the cover head against her lips. I made a decision not to touch the pump to inflate my knot. I pressed in and my fat head started to slowly split her open. She seemed a lot tighter than normal. I tried to get deeper but it was taking some effort and time. It was the best feeling in the world.

I pushed in farther fully expecting my shaft to just keep sliding in. That’s not what happened. I looked down and saw that my knot had swollen up to a big size and was trying to get in her. I had not touched the pump so this happened naturally. I now had a fully natural knot. I pushed hard and she opened up enough for me to get it in. Once in her muscles grabbed it and pulled me deeper. My knot continued to swell because I could feel the tightness. I really wanted to cum so I swung my leg over so we could stay tied and let me start shooting sperm. A warmth spread over me and I felt my cock shoot its first large rope of sperm deep inside the female dog. We were going to be there like this for awhile. Suddenly the front door flew open and standing there was my girlfriend taking in the scene in front of her. I was completely naked and my cock was buried inside her female dog. We were firmly stuck so there was no escape. I just looked back at her. She said,”What the fuck are you doing to my dog?”

I had been caught red handed. I just hung my head and said,”I can explain.” She said, “ Fine , explain but get away from my dog first.” I said,” I can’t because we are stuck together.” She said,” What the hell do you mean stuck?” I said,” My cock is really deep inside her and its very swollen. It won’t come out for some time. We will just have to wait.” As soon as I said it my cock erupted again and shot my sperm deep inside. I closed my eyes and shuddered. She noticed and said,” What did you just do? Are you cumming? Did you just shoot your cum in my dog?” I said “ Yes I did. It will happen a few more times before we are done. I have no control over it. Once I finish cumming my cock should shrink enough for me to be able to pull it out.”

I guess she didn’t like that answer. She started yelling and cussing and pacing around the house. I tried to drown her out so I could finish shooting my sperm inside the dog. It would take awhile longer to be drained. About 15 min later she came over to us and said,” So are you finally finished shooting your mess in her?” I felt a couple of small twinges and just said,”Almost.” She just said,”Well hurry up.”

I felt the female dog pull on my knot to test it and I figured it was time to try and get untied. I had no idea how big my knot was because it had swelled up on its own. It could be max size. What ever size it was my girlfriend would see it and be shocked. I rocked back and forth trying to get some movement and it wouldn’t budge. My girlfriend was looking down at where we were tied. There was just a small piece of my shaft sticking out of the dogs pussy. The rest including my swollen knot was firmly stuck inside. I continued trying to pull but wasn’t making much progress. My girlfriend went into the kitchen and then stood over us. Suddenly she dumped a large cup of ice water directly onto my balls and precisely where we were tied. I said,” Oh Fuck.” It took my breathe away and right before I knew it she dumped a second big cup of ice water in the same place. Neither me or the female dog like that very much. We both started to pull and the knot started to emerge. It came out slowly and I heard my girlfriend say,” Oh My God.”

As my knot emerged I could tell it was huge. Probably softball size. To see that come out of her dog was probably pretty scary. Soon we had cleared the thickest part and the rest quickly followed. My cock slowly was squeezed out and was still fat and heavy. She led her dog to the backdoor and let her out. I slowly stood up but had to sit down in a chair. My cock and balls and knot hung down low between my legs. My girlfriend got a chair and sat down across from me. She asked,” How many times have you had sex with my dog?” I just sighed and said, “A Lot.” She asked,” For how long?” I just said,” About a year.” She asked,” 100 times 200 times 300 time?” I said, “Yes Yes Yes.” She asked,”Did you shoot your sperm in her every time?” I sighed and said,” Yes every time.”

I saw her staring between my legs. My junk was on full display and she couldn’t take her eyes off it. She said,” What happened to your cock? It used to be so nice and now it doesn’t even look human.” I looked down at myself and was shocked to admit she was right. Things had changed. I had been ignoring things but now realized how different I looked. The first thing I noticed was the color of the skin my cock balls and knot were all a deep red. It was striking. My penis was bigger and was shaped differently. My foreskin completely covered my glans and was so tight I could not pull it back. This made the tip of my cock more pointy. The overall shape just didn’t look human. There were large and small veins crisscrossing all over it. It has spent a lot of time inside the dogs pussy and that must have had an effect on it. Of course the most prominent thing was my knot. It allowed me to tie with the female and had originally been a manual process but now seemed to function on its own. I actually liked the way I looked now.

She said,” if I had seen a picture of you I would swear that’s a large dog’s cock.” I was fine with that. She then said,” About 10 days ago do you remember having sex with my dog?” I thought for a moment and said,”Yes we mated.” She asked,” Do you remember anything different about her? Anything out of the ordinary?” I counted back the days and then understood what she was getting at. I said, “Yes she was in heat. She gets very horny and frisky when that happens.” She asked,”Did you shoot your sperm inside her like you did here today?” I just stared at her. Something had happened. She said,” So when my dog was in heat and at her most fertile you deposited a load of sperm inside her. I just nodded. She said,” Well then congratulations. You are going to be a Daddy.”

I just stared at her but somehow I knew she was right. I was the Father. I didn’t know what to say so I just kept quiet. The dog was my Mate and was now pregnant with a litter of puppies. My puppies. I had secretly really wanted this to happen. I think this was what my body had changed for and what drove my desire. My girlfriend had just been sitting there waiting for me to deny it but I didn’t. She then said,” Are you getting an erection? Is this exciting you?” I looked done and sure enough my cock and knot were swelling and growing. Completely involuntary on my part. It was happening quickly and I was huge. She got up and walked over to me. She reached down and tried to take my cock in her hand. It was too big for one hand. She felt the knot and how hard and big it was. She then told me I would be expected to help out with everything to do with my mates pregnancy including the birth. Once the puppies were born I would help raise them until they were old enough to be on their own. She would select the biggest Male to keep and raise. I would train it to mate with her and become her lover. Since my mate was pregnant and shouldn’t be bred for a few months I would have to use my cock on her so that she could get used to being bred by a dog. Not the outcome I expected but one I accepted. She then took my by my now fully erect cock and led me to the bedroom to start training.

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