Do I go for it?

So I’ve been hanging out with this boy for about a month or two now. He has a girlfriend and I didn’t know until 1-2 weeks of knowing him. I’ve been liking him from the jump. And his cousin said he liked me. Well, we fucked like 3 times already and I hate myself for it Bc he has a gf and I know but my feelings take over when I’m around him. I told him we can’t anymore and he agreed. But I still like him and he still has this gf. They started dating whenever school might have started or a little after. Do I try to go for him or just try to get over him? Like should I talk to him abt it and see how he feels? Idk life is so stressful.