Do I talk about what I did while we were broken up?

Me and my boyfriend broke up in June. There were a lot of reasons why we broke up because at the time he wasn’t treating me right. In July, I slept with someone and he found out. I didn’t deny it because we were broken up and I didn’t think we would ever get back together. Me and this dude hooked up a few more times over the next few months but rarely because we live far away. Me and my ex recently got back together and things have been a lot better. I have blocked the other guy and completely cut him off because it was just a couple flings there was nothing there. I think that telling him will only cause an issue and possibly cause us to break up again for good but for some reason I feel guilty. He hasn’t asked any questions about it and we have been doing so much better. But what if he finds out somehow later on and gets mad at me? Can he even get mad at me for what I did when we were broken up? I didn’t cheat or even consider us getting back together. But I’m afraid of losing him. I think it’s one of those things where I should cross that bridge if it ever happens but why bring it up and cause an issue out of nowhere. I don’t know what the right thing to do in this type of situation. Is it common curtesy to tell what you did while broken up?