Should I tell my boy friend my mistake?

I have done things that I’m regretting and I don’t know whether I should tell my boyfriend about my mistake. What happened is, it was during a holidays, we were far apart from each other. I was at a party with my friends and two cousins. The party started all well and everybody enjoyed themselves including me, but almost everyone had a partner and I didn’t. I felt left out!Things started to be erotic some kissing and some having sex. I was getting bored by then.
A guy came to me and accompanied me. We talked and laughed. Then he started to kiss me and I kissed back. I wasn’t thinking straight – I totally lost it! After the kissing he pulled me upstairs to the bedroom and we had sex. I was really not thinking straight. So now when I’m with my boyfriend, who I’ve been dating for a year and we’ve already had sex, I just don’t feel like he deserves me because of what I did. Should I tell him or not?