I had something similar happen to me when I first got MG but had not started taking Mestinon. My teeth would not align properly all the time when I tried to chew or talk and this made me feel like there was something wrong with me teeth (I had a cavity filled a few weeks before so I thought the dentist did something wrong). I actually considered going to the dentist it was so bad. Sometimes they clicked together similar to what you described and it hurt. This problem has gone away now that I am taking mestinon.

I hope you figure this out.