Here's the most important thing: don't get wasted, especially in that context. It is an absolute recipe for disaster, and in no way worth it. Not to mention, if you're a minor, it's not legal.
Since neither of you can be certain what went on, I'd advise you treat it like a crisis: go see your gynecologist, doctor or clinic ASAP. Both of you will also need STD and STI screens.
There's little else we can do in terms of help with something like this, really.
Editor and Founder, Scarleteen
My epitaph should read: "She worked herself into this ground."
-- Kay Bailey Hutchinson