Who fucked up?

When we were broken up, I saw someone else. My ex (now Bf) started talking to me again and told me all about how he loved me so much and couldn't live without me. I told him I was seeing someone else but was willing to try again, but that I didn't know where it was going with guy I was seeing. He fucked his ex the next day and didn't tell me about it until after sex on the morning of our last day of our get back together vacation.  I kept seeing guy before the get back together point but broke it off before I saw my bf in person again. I told my bf about it after he told me about her. 
Guy I was seeing was poly and in a poly relationship w another girl in another state. It was casual, no attachment just great sex. TBH I have no regrets bc BF took me for granted the first time around and we weren't back together yet. 
Is it the same thing? Or diff bc guy was in my life before bf came back and bf just fucked what was available? 

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