Tell your boyfriend how you feel. You'll feel better knowing that someone knows you're a little nervous about the event. And it'll be good for you to talk about it instead of keeping it to yourself. (We're all guilty of doing that too often I think). I know it'll be hard, but try and have a good time. There have been plenty of occasions where I was so close to not going out because of my fear but I've ended up having a fantastic time. You cannot let this fear control your life all the time. Sometimes you have to tell it to fu** off! The more you do this, the less control the fear has over you.
Let us know how you get on.