go to another (reputable) dentist, tell them the tooth is giving you pain, do not go into the history and ask whether there is any indication that it needs root treatment. Ask them to check the bite. It should not cost much to have such an examination.
If the filling is too high you should be able to feel it in your jaw muscle on one side. The muscle will be tensing more on the higher side when you clench. If it feels high then it usually is.
Which teeth did you have filled ? (upper/lower, molar/premolar?) Were they both on one side and was it composite or amalgam?