It may be a sign that you need to have your wisdom teeth out. I used to use the pressure from my wisdom teeth as a measure of stress, and then eventually got them taken out.

Also, I find when I get that pressure before going to bed it's a sign that I'm going to grind my teeth. I sit up, give the jaws a relaxing rub, maybe prepare myself for some reading and the expectation that I won't be at work early next day, then have a good sleep.