Adamchuck.............Now this might be a long shot and I probably shouldn't say anything because I really don't know about his first hand but.........I recently talked to a person who was having the same symptoms as you are describing and thought for sure she had tongue cancer. After waiting a whole month to get into see an ENT and worrying like crazy the ENT peeked in her mouth and said immediately "you are taking too much vitiamin A" Now, I don't know if that is what your problem is but perhaps you are unknowingly taking something that is just irritating your oral cavity, tongue specficially. Like Marliz said, if you've been to all those Doctors and not one of them sees anything wrong, you are PROBABLY safe.
However, if you still don't feel comfortable with their opinions I suppose you could always request an MRT or CT scan to make sure. Good luck! Sincerely, Donna