Stuck in between...help please

My ex was a great guy loved him to death but he just all of a sudden tightened up an would not tell me what's wrong so we broke up an now he's apologizing an thinks it's so bad that he did this im asking him alot of questions about it an he said i did nothing wrong an he really wants me back but in the time we broke up till now i met somebody else but not dating just hanging out so what to do,do I tell both of them I need some time to think,the new guy is nice to but im not over my ex so im stuck in between so help would be appreciated