I'm going lose my virginity?

Okay so my gf and I is going spend a time saturday night she called me yesterday saying that im going have a hell of a night we're going have fun and she sounded excited and horny lol. So shes 15 too and shes obviously talking about sex and she been showing signs like alot. What should I do? Buy condoms? Birth pills what? I don't wanna get her pregnant even though i have lots of money to take care of the baby. What should I do? What do I have to get ready for? So nervous lol