What you have to understand, if you can process it, is that you didn’t do anything wrong. When a boyfriend doesn’t like something in a relationship, he has the choice to tell you what he doesn’t like and try to make things work with you, or to break up with you before he begins dating other people. Cheating is just one of the options he had, and that’s the one he took. This is not someone who wants to work things out with you. He wants you to adjust to him.
I’m sorry that you are still trying to please him. I hope you can understand that whatever the reason for his cheating on you, it wasn’t your fault, and you didn’t deserve that. Move on, and find a boyfriend who wants to work on a relationship with you and respects you enough to not cheat.