I have a boyfriend and I'm very much in love with him BUT for some reason all the people I used to have crushes on have been popping up in my head and I don't like it, it makes me nervous

This isn’t uncommon at all. Your ocd is trying to make you feel like you have feelings for someone else when in reality, you definitely love your boyfriend much more. Whenever they pop into your head, just let them sit there for a while. Don’t fight off the thoughts or run away from them. If you just accept the thoughts, your ocd will think you’re not bothered by them anymore and start to leave you alone. It’s very hard, but I know you can do it! Your feeling for your boyfriend are very real and I hope you two have a wonderful relationship together!