Eat something crunchy or chewy before bed (bagel or apple, that sort of thing). Teeth grinding can be kind of like the brain twiddling its thumbs with your teeth being the thumbs. Wear out your jaw with chewing and it won't need/want to be so restless. What's got you being so stressed?

My dentist made me a mouth guard but it was expensive and then the next time I had dental work it didn't fit anymore since my mouth had changed. I didn't like it either, having something big/bulky in my mouth when I'm trying to sleep; made relaxing even less likely :-)

Now that I think of it; I'd try chewing a wad of gum some time during the day a little ways before sleep.