My boy Friend told me how attractive he thought a girl was and I asked him to show me the picture and he did now I can't stop thinking about it? why?

Question

My boy Friend told me how attractive he thought a girl was and I asked him to show me the picture and he did now I can't stop thinking about it? why?

Anonymous

He used to jack off to pictures of girls he new from the time we started dating until 6 months in to it. Then a few months later he did it to a girl he new I was extremely jealous over. Then again a few months later it was her. Then it was one of my closest friends. Iv forgave him for all of that, but we made up for the friend thing and right after he told me in detail how attractive he thought a girl was that he used to go school with was and I asked him to show me a picture and he did, she was standing by an ocean, and now every time I see water a lake ocean sea I can't get that image out of my head. And it was on Facebook but thing was it didn't just appear in his news feed she posted it along time ago witch means that he was thinking about her and sherched for a picture of her. But my question is it was about 4 months ago, and I can't get it out of my head, and now its starting to break us apart. Even though I kept him when most others would have left, I just can't seem to actually for give him for this one.