You'll get over it sooner than you think. I had the same problem but since getting past it, I would not trade my time on stage in front of a big crowd for anything. It is by far the best natural high.
Sounds like you haven't convinced yourself you are GOOD!
Playing and singing is a gift many, many people do not have. However, it's for sure many, many people appreciate music and that's why they are there; to see someone do what they cannot and to hear the magic.
Before you perform, close your eyes and become part of the audience, imagine sitting there with them, watching yourself on stage and hearing the fantastic music you create. Then open your eyes, smile really big and show them you are having a great time with them.
It's the time of your life!
I once thought a "Sweeping Arpeggio" was an Italian janitor.