<human>: Provide a brief overview of the text.

My girlfriend and I were friends for a few months before we started going out, and as friends I found out a bit about her sexual history, which I never really had an issue with... until we started dating. I've only ever been with one girl before her and that was when I was 18. Her history is longer, fuller and something that makes me feel a little bit ill every time it's even mentioned in passing. 

Every other part of our relationship is great, I just feel like the sex is lacking and that she doesn't enjoy it that much. She's never had an orgasm and says she wants to have one but has never really tried by herself and seems against the idea of trying now.

These two things joined together have left me feeling just a bit useless when it comes to anything in the bedroom, so my question is essentially: how do I stop feeling insecure about these things?
<bot>: Girlfriend has had more partners than me, also has never orgasmed (and doesn't seem especially aroused during sex). Add these together and you get me feeling pretty rubbish about our sex life. What do I do?