I too clench my mouth , sometimes I massage it to relax it.
I used to grind my teeth (in my sleep) when I was under extreme stress but I don't think I do now as my partner hasn't said so??
jaw clenching and tooth grinding are common for anxiety sufferers, can lead to TMJ, details on the net, the sore jaw mucle pain can seem to come from behind the eyes
a beta blocker med may help
a football mouthguard or splint from dentist can help if these problems happen at night
the grinding often causes tooth and filling problems