I need honest if even brutal opinions

So me and my boyfriend broke up, he kicked me out but we ended up getting back together the next day but the night he kicked me out I went to my exes house and we'll you know stuff happened...but he didn't do anything with anyone while we were broken up...should I tell him and did I cheat on him? It just feels like I did..we've been together 2 years. I mean I don't know if I should tell him and ruin the relationship, because we weren't technically together when it happened. Idk. I need opinions