You could have cracked your tooth. Have you been eating anything hard latley. Or if it is a top tooth, sinus problems such as a cold could cause it.

Maybe you have a cavity.

I have the same thing.. I went to the dentist and he could not find anything.. It went for over a year.. I said something to him about it and when i was in getting another filling in a adjacent tooth he removed that filling to find.. A cavity under the old filling.

Well here I am 6 months later and Still, same pain in that tooth when I press down only in the morning when i wake up.. once i press on it.. rest of the day is painless.. So when I go back IN a few more months.. Hes going to check it again.. I dont think he got all the cavity out.