I would see an orthopedic doctor to have panoramic Xrays done to see if there is damage to your joints. Also I would have a mouth guard made for grinding your teeth as that is usually why people have TMJ and its usually at night however some people clench also during the day.
Do wait to long as I did and I shattered my articulating disk in my jaw and had to have surgery. This is one surgery you dont want to have. It is worse than child birth.
This sounds like TMJ.
I would recommend seeing your Dentist to get this checked out.
He will be able to recommend jaw exercises that you can do to help and also possibly refer you to a specialist who deals with TMJ problems.
A good medication to try for TMJ pain is amitriptyline, this works by relaxing the muscles which spasm causing the pain.