Alright guys, I need your experiences. Have any of you dealt with fatigue before? If so, what was the cause?

I finally got a hold of my dickhead doctor and we have ruled out thyroid issues. Even though I asked him to do a bunch of blood tests (I pay a lot for insurance and I've already hit my deductible so), he really did not do very many. I am going to go see a primary doctor now to get some more tests and I would like to go in armed with potential causes or more information so I can ask for tests to be done instead of assuming he will just know what to test for. Any personal stories are greatly appreciated!