Start telling yourself you do have the confidence to get up in front of 1000's of people, say it, believe it and mean it. If you start changing how you feel about yourself and talk to yourself about competing on stage you start to actually think its true vs falling victim to your own self doubt and uncertainty. No you cant avoid all risk or nervousness or even the possibility of failure.......being ware of it is healthy and normal. It shows you care about the outcome as you should. However seeing past that and looking at stage time as your time to seek success and opportunity, strut your stuff, show off the world what you have accomplished etc......that is what needs to pervade your mind. Give your avi if you look like that now or any bit better, you have soilid foundation to run with as as being competitive let me say that much.
Good luck to you and welcome to TID!