Sex Scale

Me and my boyfriend have been dating for almost 2 years now. We've been having sex for about a year and a half and recently I asked him if I was good at it? I've only ever had sex with him but he's had multiple partners. On a scale of 1-10, he told me I was a 6! I was bummed because I thought we had a better sex life than that.. I don't know what to do now. I feel like I don't fullfil his sexual needs. It sucks knowing that he's had better and I feel like he'd rather be with them. Any tips that might change his mind?