Bruxism. How do I stop clenching my teeth?

I have this problem with clenching my teeth. It seems to be pretty involuntary and I often wake up with an awful headache because I do it while I am asleep. I try really hard not to (obviously) and I chew gum whenever possible to prevent it during the day but its getting out of hand and I am plagued by headaches because of it. Has anyone else found ways to deal with it?