Check out the film for "Singing In The Victory"
https://www.youtube.com/watch?v=fXH60qrJHus
http://www.austinstoneworship.com/development - In this video, worship leader Jimmy McNeal, gives some encouragement from Scripture to worship leaders who lack confidence when leading worship.
Here are a few points from Jimmy's explanation:
1. When you lead worship, you can lead with confidence knowing that God has entrusted you to lead those people.
2. When you are tempted with doubt, you can be reminded that it is by God's authority that you are able to stand and proclaim the excellencies of Christ.