TMJD and running

I've been having jaw pain since two Thursdays ago--i.e., coming up on two weeks. The pain started after a tempo run, got better for a day or two and has gotten progressively worse since then. E.g., I couldn't open my mouth wide enough to fit a sandwich into it. It was that painful. I saw my dentist today. He said I have TMJD from clenching my teeth and, possibly, from grinding at night, although he thought it was less from grinding, as I don't have much wear. He wants me to put my tongue between my teeth while I run, so that I won't bite down. An interesting tidbit is that when you chew food you apply 200 to 800 foot pounds of pressure to your teeth. When you sleep or are otherwise engaged in something other than eating (like running), apparently you can apply up to as much as 2,000 ft lbs of pressure. He wanted to give me a prescription drug to relax the tense muscles and guessed that I was 120 pounds. That's because he couldn't see how muscular I was under my clothes. I'm actually 145 to 150. :-D