Girlfriend

Okay so I'm a girl and I've been with my girlfriend since we were about 14/15 and now we are a little bit older now. Anyway, so I feel ready to have sex, however I'm very scared, I feel like I don't know what to do. I'm scared I won't give her an orgasm or I won't do it right and let her down. Do you think she's feeling the same way? We are both virgins and before we started dating the most we'd done with other people was a kiss.