Find a practitioner you trust (whether it's an MD or a naturopath or whatever) and have him/her evaluate it. After all, letting the doctor (of whatever flavor) figure out what it is doesn't mean you have to agree to whatever treatment s/he suggests.
Once you have some idea of what it is, then you can decide how to handle it. But the first thing to do is to find out what you're dealing with, and that's true no matter which course of action you take, so start there.