How Do I Talk to An Ex-Boyfriend About His Cheating During the Relationship?

My boyfriend and I dated for 3 years before we broke up late last year. This summer (7 months after our breakup), I found out that he cheated and the reason why I found out was because the girl had been telling people about how they had messed around on a trip (I didn't go because I had work). He went on the trip and cheated during summer and we broke up in the fall. I am unsure what happened to them in between the time. I know who the girl was and in fact, I know her family and her friends. I recently had the chance to meet up with her family and friends and they all know about it. I had the worst time in the gathering and it felt like the pain just never went away and I just never moved on. I am still in so much pain from this past relationship. Although he had asked to work things out and although I wanted to work things out with him, I just cannot forget about all these pain and lies that he told me. Even until the point that he broke up with me, he had told me that he was 100% faithful and never cheated and the reason why he had to break up with me was because he did not want to cheat on me. It's been so painful and I'm still in so much pain. Can someone please help me? Should I confront him about this? And if I do, how? It has almost been a year since the breakup and I am still in terrible pain. I'm still crying so much over this relationship.