I used to be exactly the same and felt like I was going to throw up in the lead up to being on stage. But once you're out there you'll be fine. All you need to think about is giving the best performance you can. And enjoy it!
All good thespians get nerves, you will be brilliant I am sure, when you come off stage, you will want to do it all over again no doubt! Break a leg (as they say).
I shall be in exactly your position in a couple of weeks.
Go through your lines in your head, find a quiet place to focus before you go onstage, concentrate, trust in what you have done in rehearsal, have confidence in yourself and most of all enjoy it.