Chipped my tooth?....?!

Two years ago, I chipped my "fang" tooth. My tooth hurt and was sensitive to touch, liquids, and sometimes food so I went the to dentist. He filled my tooth and it felt fine. A few months later, the filling became rough and the pain started back up. It feels like it has to do with the nerve. I went back to him and he said nothing is wrong so I went to another dentist. This dentist filed it down (which hurt) and said nothing looks wrong. I am still in pain and I am confused because both dentists tell me that there is nothing wrong and that there is nothing to fix. In my opinion there is obviously something wrong and I don't know what to do. Please help!