have you ever had trouble forgetting a mistake from your bf

I would like your opinions girls, me and my boyfriend have been together for a year and 2 months. He’s literally the perfect man, he’s so sweet, would do anything for me, cries if he has the worry I’ll leave him, brings me cheese and wine, cuddles me, loves me and tells everyone how much he does and I love him more than the world but one day I saw on his phone on a night out drunk he brought another girl a drink and then searched her on Facebook and asked her to meet up with him and was begging it off her. I was upset, nearly broke up with him. I was just so shocked and upset. I forgave him but it’s like I cant forget, I bring it up when I’m upset and when he goes out I end up worrying and arguing with him and I feel like I’m pushing him away. He says it was his fault and he understands but I can’t help but feel like I’m being a bad girlfriend. I wanna forget and be with him but I’m beating my self up constantly but making my self think I’m being a bad girlfriend and bringing it up. How would you say I’m reacting ? Am I in the wrong