Ok....I experience what you do..... I think.
I usually notice Im grinding my teeth and clenching my jaw when my anxiety has got the better than me.I catch myself doing it and tell myself to stop but to no avail.
My gp says its a sign of severe depression....I think its anxiety.I dont know which is correct but I actually chipped my front tooth a month ago.
Talk to your pdoc or gp about it.....maybe its anxiety and they can suggest something to help.
It will be interesting to see what he/she says....good luck!