So long story short, I’ve been talking to this guy for a few weeks and I slept with him a few days ago. I just found out he has a girlfriend from one of his friends. I haven’t brought it up to him. Should I mention it? Or just cut him off? Find his girlfriend of two years and tell her? Because if I were her I’d want to know. But I also don’t want him to hate me and if possible I’d like to end it with him on good terms. Any advice?

The reason I’d like to keep it civil with him is because the university we go to has a very small campus. Everyone seems to know one another. We also have a lot of mutual friends.