Every once in a while i catch myself clenching my jaw, almost like when you're on mdma, and i have to pull myself out of it.. I'll be pulling and pushing my jaw open and closed and it results in tension headaches..
I don't know why, but clenching your jaw seems to feel good on you gums. If you had a tooth infection, that is one of the reasons why you would do that. Your jaws will hurt because your putting pressure on them, which isn't good. The tension headaches come from your muscles squeezing hard (well...depending on how hard you clench) in your jaws.