Thanks for the responses.
I don't take any other medications, so it's safe to rule those out. I'm not aware of my having TMJ, and don't have any pain in my head/face, so I have my doubts about that.
I see I forgot to mention that, for a period of about 4 months, the condition did go away. That was around a year and a half ago. It happened when I lost about 20 lbs. while I removed sugar, fast food, and caffiene from my diet. I'm still at the same weight as I was then, however I do consume sugar, fast food, and caffiene again.
I guess my next step needs to be to cut out those things from my diet again.