This hurts tbh😪😩

My ex dumped me for someone else. About six people told me they would always flirt with each other. He told me he wasn’t flirting and that’s just the way they talked. Well I told him if six people told me they were flirting then they most likely were. He said “that’s the dumbest shit you have ever said”. We dated for three years and I thought he only had eyes for me.

Is constant flirting cheating? Or not really?