Most of the population can't handle being in a relationship once they've been cheated on. Either they break up, or they say things are fine, and eventually they break up coz in truth they really couldn't handle it. Some people stick it out, only to become paranoid and suspicious. How can you trust someone who would cheat on you? I would certainly never trust you, and I don't even know you. I say don't tell because you've already DONE a terrible thing, and you'd make it worse. You aren't truly considering the feelings of your current boyfriend, or you NEVER WOULD HAVE CHEATED. You've already shown he's not that important to you. So why are you with him? It's completely unfair, you're being selfish. You might as well tell him and break up with him. It'll be better that way than a random breakup, he'll be able to be angry at you and get over you quicker.
And you DO think your ex still loves you. You want him to love you, you need to know that he broke your heart and regrets it so you can feel some sort of validation. Well, he's not a good person either coz first he broke your heart, then cheated on his new girlfriend, then starting messing in your life again. Maybe you guys really are made for each other.
It's going to be a long and painful process getting over him if you can't get away from him. Your friends should understand if you need space or can't hang out when your ex is there. And I'm sure the temptation, having already been fulfilled once, is more likely to happen again.
I think you need to face reality. I'd love to help and give advice, but you aren't thinking logically, and you aren't doing what is right.