Hi Jennyflame,
It appears that your bite may have shifted. Frequently this means that the disc within the joint has been "caught" outside of its usual position or has been damaged/stretched/trauma. You now need to treat your jaw like it has been sprained. Use lots of moist heat and ice directly on both jaw joints (right in front of your ear). Take up to 800 mg. of Ibuprofen (with soft food) if you can tolerate it. Try not to use your mouth as much as possible for a few weeks - eat softer foods or liquids, talk as little as possible and no gum chewing or wide yawning, etc. Evaluate how you are sleeping - do NOT sleep on your stomach. The back is the best but with a good cervical pillow you can sleep on your sides but don't put your hand under your face and don't stretch out your neck while sleeping.
You need to relax big-time and you might need something like Valium to take at bed-time for a couple of weeks. Or a muscle relaxant. Have a friend or someone give you shoulder and neck massages if you can. Hot tubs are very relaxing.
The grinding or clenching must be stopped right away. I wouldn't be surprised if this caused the "trauma" to your jaw. If you know that you are gritting, you are probably doing more so during the night while you sleep. There is a rule that we should never bring our teeth together, and while in resting position, the tongue should rest on the roof of your mouth, teeth apart, lips together (relaxed and can be slightly apart). Think about keeping the jaw, neck and shoulders down or relaxed. One person I know "cured" his clenching problem by keeping his tongue between his teeth. I don't know if that is good for all, but it worked for him.
I'm running out of time, but also evaluate your posture (check out nismat.org/ptcor/tmj) and add Super Vitamin B Complex and Magnesium to your daily diet. Relax anyway you can. Stress is the number one enemy of TMJ. Please ask all the questions you want and hopefully we'll all be able to help each other.
God bless...
Carol