6 months ago, I went in for a cleaning and was told I had developed decay around an old fillng. I had the tooth filled( 1st molar on the upper right side after the wisdom tooth) and afterwards I had pain if I tried to bite down on the tooth. I had it adjusted several times, but the pain continued only when I bite down. So my dentist told me because it was a large filling, it was too close to the root, and that caused my pain. So I went to an Endodontic Specialist and had a root canal. I had no infection and the specialist said that my tooth had no cracks. In a week my tooth completely stopped hurting, and I could chew on that side. I went in and and was fitted with a temporally cap, that didn't feel as good as my real tooth, but didn't hurt. When my permament crown came in they had to glue it on twice in the office, and it later popped off the next day. They reglued it again at the office, and it popped off in the office again! They reglued it once again with really strong glue. It feels like it is flexing on my tooth, and it still hurts when I bite down. I have had it readjusted three times, and now he is telling me to go back to the Endodontic Specialist, because he doesn't know what's wrong with my tooth. The tooth only hurts when I bite down, and sometimes the tooth under it hurts. What do you think it is, and do I need a second opinion? Thank you!