I think I cheated on my ex

This has been eating me up for so long now and I don’t know if it would be considered cheating or not and I just want to tell someone and get their opinion. So I used to date this boy and we were lowkey kinda toxic to each other. I would always start arguments because he was a shitty bf and did shitty things to me and I’m pretty sure he’d cheat on me as well and I knew because I secretly logged into his accounts behind his back but I never told him I knew abt him cheating because my self respect was so low back then and I genuinely thought he was the loml. Cheating never came across my mind until maybe the last few weeks of our relationship which by then we were barely talking to each other but we were still in a relationship. I added this guy on snap and we were talking and kinda flirting. He’d call me cute and stuff and he sent a pic of his abs (no we didn’t exchange nudes). Eventually me and my ex broke up because we both realized it was going nowhere and I was fine with that. But whenever I think abt my ex I wonder if that was cheating even though we were pretty much not even talking at that point. To this day he doesn’t know about that guy