Sexual insecurities.

So today my boyfriend told me that I'm the best sexual partner he's had. He's had sex with quite a few women, and he's only the second guy I've slept with. I'm really insecure about my sexual ways, the guy I lost my virginity too told me I sucked in bed and just said a lot of mean things about me and sex. Part of me doesn't believe my boyfriend but I want to. I just can't seem to get rid of the thought in the back of my mind that I'm horrible in bed and he's just saying I'm good to make me feel good about myself... I sound so bitchy I know but I just don't know why I'm so insecure when it comes to sex.