I Can Never Unsee This

Early on in our marriage I had become very confident in my sexual prowess. I could almost always make my wife orgasm, I would go down on her and get her close and then start fucking her and most times she would orgasm. She seemed content.
One weekend we had a guest and we drank some but also had some pharma, we were getting a little loose and watching a dirty movie. Not porn but lots of nudity.
My friend and my wife were getting flirty, talking about the actresses tits and bodies. She tells him she has had a boob job and ends up showing him, and then letting him feel. She really feeling good and says he needs to show his dick and he does. His dick is really big compared to mine and things began to escalate. Seeing her handling his now hard dick, putting two hands around it and looking at me saying “wow, that’s really big.” She gets me to get naked and I was already hard from seeing her handle his dick.
Without warning she leans in and starts sucking him and me back and forth. Commenting all the while that she could easily take mine all the way down but no way with Steve’s. He was several inches longer and much thicker, we're on the sofa and she is between us and I start to touch her pussy and it’s soaking wet. She immediately pulls him over on her and he’s in between her legs with his knees on the floor. She reaches for his dick and rubs it up and down her pussy a few times and then he’s pushing in. Slow, slow she says and in about 30 seconds she is having an orgasm. In another couple of minutes she has another and he is pounding her now. I had never seen her so aroused and the way she talked to him was something I had never heard her say. Soon he starts to cum and tries to pull out but she locks her legs around him and they both start cumming.

We never did this again after this weekend but I’ve never gotten over how easily he made her cum and so many times. They fucked all weekend, I was only slightly involved. It wrecked our sex life for almost a year, I could not keep from cumming prematurely. Visions in my head of him fucking her would make me cum and I couldn’t get rid of them.

Now many many years later those memories are the only thing that gets me hard. My wife is not into sex any more so I masturbate a couple of times a week, always picturing her being fucked like I could never fuck her.