It appears that you and your girlfriend have already discussed the possibility of having sex. That’s a great thing to do before getting caught up in the moment, especially so you’re prepared with all you’ll need to practice safer sex. But, before you start having sex, talk to her about how you feel about your lack of sex experience. You’ll most likely discover that she doesn’t mind and still wants to be with you. But, in either case, there’s no better way to become closer to someone than to be completely honest and transparent about your feelings. It’s even more enjoyable than sex.