New relationship dynamic

My girlfriend and I adopted a dog and now I’m the third wheel.

My girlfriend and I are both in our mid twenties and are moving in together. She is a a taller than average athletic build with nice c cup breast and large hips while I’m a more lanky build. Before we both lived with our respective families so alone time wasn’t available really, but when we did get intimate, we both had very perverted ideas. She would often finger me and use her dildos on me. We had normal sex too but we experimented here and there. Something I’ve never told her is that I have some slight cuck tendencies, more like watching her masturbate rather than her being fucked by another guy. I also have a zoo fetish I keep very quiet. Mainly with male dogs.

When we moved in she really wanted to get a dog, I didn’t really have a preference and she had experience training and taking care of dogs, so I let her choose who she wanted. She came back with a very large mastif named Benji, like nearly 200lbs, which was more than both of us weighed. I can’t lie when I saw him for the first I felt a little tingle, but I pushed those feelings down. About 4 months go buy and these feelings towards him keep coming up. There was a time where I find him in the back yard mounting some random dog that got in and when I tried to separate them he flashed his teeth so I backed off. Once he finished up he just looked at me, fully hard, his unsheathed dick must have been at least 8 inches with a knot the size of a tennis ball. Another time I woke up to him fully on top of me licking my face, his weight kept my arms pinned so I couldn’t stop him, I was like that for at least 5 minutes of him slobbering on my face. His tongue made my heard race and when I checked later I was leaking down there. I never mentioned this to my girlfriend, and she carried on doing whatever training she did. This culminated on one day where I was alone with Benji. My girlfriend said she was coming home late so I had to do his nightly routine. I let him outside to use the bathroom and when he came back in he started licking himself in front of me. I thought nothing of it until he started getting harder. My heart was staring to beat faster. Months of watching him was making me feel something. All of the sudden he stopped and just stared at me again, his dick proudly shown. I felt like I couldn’t hold back anymore, I had to try something. I called him over to the couch and started rubbing his sides, I started to inch my way towards his dick. I couldn’t get to it too good so I made the mistake of moving to the floor. All of the sudden he jumped on top of me and his bid dick was right infront of me. I had to fully grab it to stop him from getting my face. He started fucking my hands like there was no tomorrow. Every time I tried to move out of the way he pushed me into the couch and repositioned. All I could do was use my hands to keep his dick away. I was painfully hard by now but there was nothing I could do about it. His dick in my face was like a dark fantasy come true. I started to feel a his knot pushing against my hand, I tried to make one last attempt to get out but he thrusted into me hard. He let out his massive cum shot all over me, ropes splashed my face and chest. It covered me in his mark. I still couldn’t move so I just had to take it all. It definitely turned me on a lot but I was still afraid to admit it. I heard a voice from across the room “Well that was a lot.” I felt the color in my face drained as I realized my girlfriend had come back. At this voice Benji unmounted me and trotted over to her for affection which she happily gave. “I-I… it’s not-“ I stammered out, I thought it was over till she looked up at me and smiled. “Oh baby don’t worry, this is what I planned.” She said. “Planned” I said in my mind, unable to fully process what that ment. “Go take a shower and come to the bedroom.” She told me, and that definitely felt like the next step for me at least. When I was done she was on the bed with her phone. “Look at this.” She told me while showing her screen. I couldn’t belive my eyes, it was photos and videos of her having sex with a dog, not just her family’s dog I’ve met. But a bunch of different ones. “I love dog sex if you couldn’t tell. My grandparents had a side business where they would train dogs for sex, and I got hooked on it when I would visit them.” She had this happy look on her face as she was reminiscing. “Benji is one of the dogs they trained, of course they don’t know that I’m the one who got him.” She had done this on purpose? She got a sex dog, “but why?” I asked. “Because I wanted to have fun with you too, plus his massive dick makes be feel amazing.” She said this as she scrolled to a video of her having sex with Benji. Her screams of pleasure were all I could hear from it, “but one thing I had to train Benji for was getting with you.” She said as the audio of her orgasming filled the room. “ I would wear your cloths while pleasing him, your cologne. He now associates your smell to sex.” A lot of thoughts and questions filled my mind, but only one surfaced. “What happens now?” I said meekly, holding my towel up. “Now the real fun begins baby.” She said almost too sweetly, “now let me put this on you,” she reached around and brought out a collar and leash. “Wait why do you want that?” I ask, “because I’m going to train you now baby, now you’re going to behave right?” She said as she opened the collar. I could stop now, I can leave and none of this will matter. But I didn’t want to leave, all these pent up feelings had gotten too much to handle. I nodded yes to her. She giggled as she put the collar on me. It’s thick fabric gripping on me tight, the leash she connected was firmly in her hand. “Good boy.” She said sweetly. “ now sit.” She said confidently, I did so slowly. When I was on my knees infront of her, looking up at her massive smile. “Good boy, now it’s time to get mommy ready, take off my pants.” She ordered, and I did so. I could already see her pussy leaking through her panties, “come on boy, lick it up” she said, I started to do what I normally did by kissing it when I felt her yank the leash, I jumped a bit at the sharp choking feeling. “That’s not how doggies kiss right baby?” She said softly, “try again”. I got the idea, I licked her with these deep, long strokes. Her juices tasted like strong, like they were super concentrated, I felt her rock her hips and heard her softly moan, the leash still pulled taught. After a few minutes I heard “stop now.”, I pulled away and looked at her “ seems like you need an example baby, of what a really good boy looks like, Benji!” She called out, I heard him trot over from another room, and at the meer sight of him I got hard again. She must have noticed because I heard a small chuckle. She moved me to the side and patted her stomach. Benji immediately ran over and started eating her out. Her moans were much louder than when I did it. She was moving her hips like crazy, grabbing his head as his massive tongue touched every part of her. Suddenly he stopped and started to mound her, “ come on baby.” She said out of breath to Benji, i saw him push his huge dick deep inside. Her cries filled the room, he was fucking her so hard. “ kiss my face baby!” She said in between moans while pulling on my leash, I started licking her face and neck. Her moans not stopping as I saw her guts get re arranged, my throbbing dick was begging for attention I’d never get. I felt her pull tight on the collar, choking me as Benji knotted her fully, a loud scream following as she was bred by him.his massive frame laying on her. After a while he finally pulled out and a large amount of cum poured out, that I was made to clean up. The next few days were filled with constant scenes of her being fucked by him while I watched. This new normal in my life is better than I could have expected.