When your dentist told you that you had TMJ, did he not recommend a mouthpiece be made for you to cushion it? It's possible your dentist doesn't specialize in TMJ -- some do, some don't. If you don't get this taken care of, you will grind your teeth down and crack them, so you need a night guard. Maybe even a day guard. Now, it might not be TMJ, clenching isn't always TMJ. TMJ is the jaw, clenching is clenching. See a dentist who knows how to treat this.