Long distance boyfriend kissed someone else

For context, him and I have been in a healthy long distance relationship for almost 4 years. However, we weren’t originally long distance. We knew each other for a year and dated “exclusively” for 6 months before he had to move away. I was in college during the time and I’ll admit in the beginning I kissed someone else and deeply regretted it and was afraid to ever say… I knew that I would never do it again and that I really wanted to be with my bf. I downplayed the whole dynamic as him (the guy I kissed) just being a guy who liked me and nothing more. Our relationship went on and through trials and tribulations we became so close even with the distance. We visit each other often as we are on the same coast, just a couple states apart and he became the best part of my daily life.

Fast forward, last month I found messages in his phone of someone he had known from high school and had been texting/calling occasionally for 3 months hidden as his guy friends’ contact. Originally he denied everything, which he later stated was because he didn’t want to hurt me further than I visibly already was. But I reached out to the girl and she confirmed they met up twice and shared a kiss the second time and that he “wanted to f%*#”. Eventually he took full accountability without justification. I feel deeply betrayed and in the worst pain of my life but occasionally I try to understand him and compare him to me (in my head) and want to extend more grace.

I feel like my world has fallen apart but I do believe he feels deep regret and remorse and since then he has been really reflecting and has been patient with me, doesn’t make excuses and answers any questions I have even if it makes me uncomfortable and even if it’s repetitive. It’s to the point where I know so many details that I feel like I was there. I want to eventually confess things but I don’t know if that’s a good idea right now. One part of me doesn’t want to tell him because I don’t want him to feel the feeling of hurt and betrayal that I feel right now. The other part of me selfishly doesn’t want to in fear that he’ll hold it over my head as validation for his actions. But I also don’t think he’s the type of guy who would do that. He was a really good boyfriend and a really good man altogether, I don’t doubt that. Even through this he has been my source of comfort. I’ve met narcissists and serial cheaters and there are usually signs and he doesn’t come off as such.

I really want to forgive him and start over but I’m wondering if it’s worth it since he made his decision so far in where we should be sure of each other. The beginning of our relationship was a blur because originally we were both confused on whether we should take one another serious and he asked me to be his gf one random day impulsively after I asked him what are we doing. No boundaries were ever really talked about we were just two young people who had chemistry and compatibility.

I’m really self aware so trust me I know that I’m no saint. Im just wondering if the relationship could be salvageable if we start from scratch and build up trust. Will I begin to resent him? Could this turn into something new and better once we break the distance? Am I delusional? Should we both just move on? Could we?
(If you read this far thank you so much)