Cheek biting shouldn't wear on your teeth like that, or even at all. The teeth are very, very hard. Bruxing occurs with clenching forces that can exceed 400 lbs.-per-square-inch.
Perhaps the night guard your dentist made didn't help, because it wasn't made properly. Many dentists think they know how to make good guards who don't.
Combine Gabitril with Lamictal, Lexapro, or Welbutrin and see what happens. In the meantime, if medically safe, some Clonidine can help a lot. Klonopin can also help a lot, but the effects wear off within about two months. I'd go with the Clonidine. You will need to see a psychiatrist to get these meds.
This combination has stopped my teeth grinding, improved my sleep, and made my jaw feel normal again.
You also need a sleep study done, and you need to see specialists to test
At the same time, you should explore the possibility of other diagnoses with the proper specialists.
