I have a fetish that revolves around my girlfriend with whom I have been with for 7 years, she had strayed a few times during this 7 years and I know about it, the first time she cheated I got to know about this I was devastated we fought a lot and after one such fight while all the moments of her with that other guy played in my head i masterbated, and since then I have a fetish of imagining her with all the guys she has cheated me with, I am not OK with this I feel sad and angry that she did something like that and playing this again and again in my head is terrible but it has become difficult for me to get a orgasim without such thoughts(imaginations).