There is a possibility that he can be cheating on you if he hasn't done anything about it. However, don't make that an assumption just yet. There can be a ton of reasons why, for example: He might not mind it; He could've been through it before; He could be doing the same thing; Or he might just not find anything wrong with it.
If it does turn out that he is cheating on you, it won't be right of you to make a big deal out of it. You did cheat on him with 3 other guys as to what your question says. I just suggest that you stop cheating if you really do love him. I'm guessing that since you are cheating, then he isn't enough for you and that you should just leave him. But hey, it's your decision overall.