Yes I would say that TMJ is definitely a possiblity. It would be a VERY GOOD idea to at least get a mouth guard and try it out. If this does "fix" the problem then that would save: 1. visit to the dentist, 2. having the dentist make a mouthguard ($200-$300) - yeah mine was $300 I believe although insurance paid all of it
The pain you are describing though is classic TMJ pain. If you "push in" on that area right below the jaw joint below your ear and then shift your jaw out and side to side you should notice a nearly intolerable pain. So there are several things that you can do before resorting to seeing a dentist.
1. don't freak out (I know easier said than done)
2. buy the mouthguard (at CVS, Walrgreens), there are many different models usually around $20-$30
3. take an anti-inflammatory (ibuprofen, Aleve(naproxen) - whichever you can take. You may have to take a pretty heft dose to get the inflammation down like with ibuprofen (400mg 3-4 times/day but try not to go over 2400mg/day total) If you get stomach upset/burning just decrease the dose. You should also take an anti-inflammatory with food.
4. try chewing on the other side for the time being until the pain decreases
5. get a heating pad/moist heat pad and place it on where the pain is
6. DO NOT CHEW GUM for awhile (this will completely aggravate things as I have learned the hard way)
7. try to deal with stress in a more positive way (stress will cause you to grind your teeth)
8. Let us know if you are on an anti-depressant (some of these will actually cause Bruxism(grinding of the teeth)
9. see a dentist if you try these things and the pain is not going down
Let us know your progress and if the pain is going down. Hopefully these things will help and you can avoid going to see a dentist who would probably end up telling you the exact same thing but charging a nice fee