Many health care professionals will tell you that it doesn't exist. But in my opinion, you can't go from having perfectly functioning adrenal glands to adrenal failure (a "true" diagnosis) without a stage in between. Medicine is funny like that. You can do a search on adrenal fatigue, I don't know if I'm allowed to post links. There's a wealth of info on the internet, but don't rely too heavily on that. It's a controversial diagnosis, much like "fibromyalgia." My opinion is that when you stress yourself out, you screw up your cortisol levels. Once they normalize by keeping a consistent sleeping pattern and allowing yourself adequate rest, you should start feeling better. Sometimes I think doctors jump too quickly to "adrenal fatigue" when it's just good ole "sleep deprivation."
Good luck, let us know how your appointment went.