I need advice, help please !

So my boyfriend and i broke up around February and he started talking to someone right after but then a lot of drama happened between me and her and he stopped. But then continued to again in june. I decided to move on and i did but in july i slept with someone else. i feel so guilty and horrible and just ashamed for doing it with this other person. he found out what i had done because we had started talking again early august and he was heartbroken, he did nothing with the other girl btw. we still have so much love for each but he is just so hurt. i want to just make it up to him but i’m not sure how i could. any ideas ?