I don’t know what to do

So my boyfriend broke up with me around a year ago. It wasn’t a break or anything, it was a proper break up. We didn’t have any contact at all for about 7 months. 3 months after he broke up with me, I trusted someone I shouldn’t have when I was drunk if you know what I mean. I have regretted that night and it haunts me, I believe intimacy should be shared with someone you love, and it plays constantly in my mind. Anyway, my boyfriend and I started talking again 4 months after that incident and we talked it out, took it slow, and got back into a relationship a couple months ago or so. I haven’t told him about that incident because I know it would hurt him and he wouldn’t understand. I love him to pieces and I know he’d look at me differently, I know I do. I just need advice, it’s eating me alive