Okay.. me and my girlfriend have been dating for a month and she's had sex before and I haven't but she wants to have sex with me and we tried but I couldn't get hard.. whats the deal? Or better yet why can't I get hard? Please help

Are you able to get an erection when she is not around? If so, stress over your first encounter is probably the culprit. Try again. The fact that you were unable to get hard on the first try can be a sign that she is very special to you. It will get better. Learn how to pleasure her without the involvement of your penis.

I don't know how old you are but f you are very young this is something that you need to talk to your father about very soon. It could be very important that you do.