Can someone give me advice about what should I do?

I cheated on my boyfriend two months ago and ended up with the guy I cheated him with.My(now ex)boyfriend never found out about my infidelity,although I thought he did.I broke up with that guy and told my ex boyfriend what I had done,not because I wanted to be with him,I just wanted him to know that I know I hurt him,and that I can't be happy knowing that.He wanted to meet up and when we did,he told me that he still loves me but he's on the way of getting over me.At first I felt at ease,but then the guy I left started begging me to make up,so we did.But we broke up again,it just couldn't work.After having some time alone to myself,I find myself thinking about my ex(the one I cheated on),about the songs he played to me,our jokes and conversations,his weird expressions...I just can't seem to stop thinking about him.So tell me.What should I do?Should I just let it go,because if I try anything I'll first have to tell him the whole truth?Or should I call him up and talk to him?I would ask a parent,but,my parents are dead,and I live with my grams,she's kinda old so I don't feel comfortable talking to her.Please.Someone tell me what to do.I just wanna make things right.For me and him.I don't want to be this person I've become.You guys are all I have.