I have this problem too! I had braces a few years back for severe jaw pain from it (they never fixed the problem because the muscles in my jaw were too strong...my mouth is very screwed up now because they took them off...so don't get braces just because I mentioned them). Anyway, I wear a retainer now at night. I can't talk in it and my breath smells AWFUL with it in but it does help me from breaking my teeth (that's how bad I clench them). When I wear the retainer I haven't broken one so I wear it a lot now. As for clenching fists I have this too...still trying to find a way to deal with it. :/
~Ursaula~