Does This Count As Cheating and Should I Be More Angry At My Friends?

About 8 months ago I broke up with my ex. He was abusive and I was proud I did it. Throughout the relationship I thought I saw Tinder on his phone but he would either call me crazy or say it was from a while back. He admitted for the first 6 months of our relationship he was on Tinder because he wanted to prove to his dad and brother he could get more likes. I was upset but he apologised and I forgave him (probs a bit stupid I know).

Well, I found out last week that he never deleted it. He was talking to girls for the three years we dated and my friends knew. He matched with some of them. They showed me screenshots were they lectured him about it and threatened to tell me (which I'm thankful for) but they never told me. Partly because they hoped he would stop and because they didn't want to be the one to make me break up with him (I would have done earlier had I known). Yet they also assured me he wasn't flirting he was just seeing if any pretty girls liked him so it wasn't cheeting. To me that's still bad. Plus he was actively calling my nuts and saying I was seeing things when I was right all along. He did have the app on his phone.

I'm also upset with my friends. My three closest friends knew. They knew for over a year before I broke up with him. One of them my guy friend also knew he would try and get with my friends when we had a fight (they never did it) but didn't tell me because "I was worried you'd have a break down and no one wants to cause a break up". So they watched me date a man they knew all this about but said nothing?

I appreciate them trying to save my feelings and their concern it would hurt me if I found out but now its just gave me a distrust for them. Who can I trust if I can't trust my friends?
Does This Count As Cheating and Should I Be More Angry At My Friends?
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