Normally the problem is either incorrect hand position or the bow's draw length is too long---or both. Without gettin too windy I'd recommend doing a search on "form" over on www.archerytalk.com. Look for posts by Nut&Bolts. He's a real guru.

Just a short version, but if the palm of your hand touches the riser or you grip the bow in any way then your hand is not positioned right.