How to tell if i clench my teeth during sleeping? how long would my jaw be sore? how long for masseter muscle to build up? how to stop clenching?

Clenching: Your own dentist can examine you personally for signs of bruxism such as wear of teeth and abfraction. Soreness of jaw, muscles, joint varies. Your own dentist can examine your occlusion (bite) and advise you steps necessary to reduce bruxism and damage caused from it. Reduce your stress (easier said than done) will tend to reduce clenching and grinding harmful habits.