It sounds like you may have some symptoms of adrenal fatigue. A reliance on junk food and lethargy are key indicators.
It's definately worth taking a test. One of the most useful tests is the Adrenal Stress Index, available from a number of labroratories such as the Red Apple Clinic, Genova Diagnostics or Metametrix.
The harsh reality is you probably won't make much progress with conventional medicine, however it's certainly worth a work up and getting some blood work done to rule out anything serious. Speaking to an endocrinologist may also help, after which they may or may not authorise some more tests, such as a GTT, ACTH stimulation test, blood cortisol and a further thyriod panel.
All of this is useful information but be expected to be told you are well. As AF is sub clinical, only physicians with a thorough understanding of how sub optimal function of the adrenal glands can contribute to chronic illness will be able to help you. Finding someone like this is rare.
If you only have a few symptoms at present you may have chronically high cortisol. This is an initial response by the adrenal glands to adapt to the added stress you are under. Symptom wise allot can still remain 'hidden' in this phase, until the adrenals start to become exhausted and cortisol output drops below normal levels.
There is a significant amount of lifestyle/dietary and supplemental changes you can make even now while you are in the infancy of discovering the clues to your health. Most of this can be applied simply for good health even if AF isn't the primary cause.
Cutting out the junk food and refined carbs would be a start.
For one of the most comprehensive guides on AF that will really get your started check out this website.
http://www.drlam.com/articles/adrenal_fatigue.asp
Good luck