Ex’s and past sexual experiences. Should I tell my boyfriend?

Recently my boyfriend went to a club with a group of friends, girls and boys. We hadn’t spoken about people we had been with before we started dating. So because I knew he was going to be drunk with girls I asked him if he had a past with any of them, just so I could be aware. He said no, but a couple of days later he told me he had lied and that there was a girl there that he had got with in the past. After this I felt weird about the whole situation and was annoyed that he has lied to me about something so little, so I asked what girls he has had a past with overall, and he didn’t want to tell me, so we had a small argument. Eventually a couple of days after he told me the girls he has had a past with.

But now I have realized that I haven’t told my boyfriend about one person I have done something with over a year ago while I was drunk, because we had never really spoke about it before. I feel like I should tell him but it is something I really regret and haven’t told anyone before. I felt pressured to do it so I feel uncomfortable talking about it, but I don’t want to hide anything from my boyfriend and I feel really guilty for never mentioning it when I wanted my boyfriend to tell me about the girls he has been with before. What should I do ? Xx