I'm a bad person because of what I should have done, is my soul hurting?

I had a boyfriend since high school, since elementary school, he was very good, super nice to me, but I treated him badly because of how much was happening at that time. I know it's not right and I really regret it so much. I ended it many times because of my insecurities, but I never cheated on him. Now he has a girlfriend and he's cheating on her with me, and since I still have feelings for him, I don't allow it. I don't know what to do. Can you give me advice, please? It's hard for me to let go. favor