You are getting a lot of good advice on here about this issue.
Penis size matters only to those whom it matters to.
It does matter to some people. Those people, both men and women, are not being mature about life and sexuality in general when they have this issue. If a woman will cheat on you because of another man's penis size, it says nothing about his penis size but a lot about her psychological issues. It may have been a focus of arousal, either size or shape or whatever, or any possible type of combinations. But, it is all occurring in a behavioral situation where the person is looking for anything to focus on to enhance excitement at the time.
The same applies to men who cheat with a woman who is ________________ than their wife or gf or has ______________ that their wife or gf doesn't have. You can fill in the blanks with anything you like. I've had a few women come onto me who have things that I could fill those blanks in with, but I've never cheated because what they have to fill those blanks with is not as good as a mature relationship.
I've been in those shoes as a man. My wife cheated on me with a man who had a large penis, apparently quite large, and yet she'd had larger and smaller penises before. Me, I'm spot on average there, but my prior wife had issues with the size (to large for her as she was quite small in that department), and my current wife who is my WS also had issues with painful intercourse at times in certain positions and I learned to be careful early on.
She even made comments about penis size when she was having the affair, which I didn't know was going on, but I still remember the comments and thought it was rather unusual behavior for her.
She absolutely detested a man we both knew who commented a lot about breast size, and it was near constantly, in women and liking bigger boobs. She felt like he was degrading women when he behaved the way he did, which he was in fact doing.
So, she did the same thing, and the comments had to do with her secret affair. It was all sort of smug in retrospect. She doesn't remember doing these things, but was horrified to learn what she had said and done during this time.
The point is, she WANTED to hurt me, at the time, and she expected to use this to hurt me, then when she came to her senses without me knowing about the affair she never, ever, wanted to let me find any of this out (the affair, penis size, etc, etc.). She would have rather died that for me to be hurt by this.
When I found out their had been an affair, I remembered these comments, and , I thought and eventually said "you threw away our marriage and family for a bigger penis was that all I meant to you?" I actually was puzzled by this, because she insisted that the affair was "just about sex", "just a fuck", and she "wanted to have fun", that he was "nothing special", it was "just fucking". So, that kind of fit into the "I'd like to fuck him because he has a big cock" type of thing.
But, that turned out to be the lie, she lied to me and the counselor when she told that initial story. It was almost all lies, and she hadn't remembered the things she had said and done during the affair to me.
Here is the kicker, I thought my wife might have had the affair because she had never been able to have an orgasm with me, or with anyone else she had ever had sex with, not once, and she'd tried a lot. But once she came clean on her abuse history and her issues and fears, she began to have orgasms with me. I'm the only lover she has ever had who has been able to give her an orgasm, the only one who has even come close, and I can pretty work with her to make it happen every single time.
But it isn't the size of my penis that gets the job done. Not for her, or anyone else. It's the rest of the picture.
