What you have decribed to me sounds a lot like adrenal fatigue. I have seen a lot of clients in your person, most of which have already been tested for thyroid and hypoglycemia. However, adrenal function is at the very core of your being and adnreal fatigue is more common than most people think.
I would recommend getting an Adrenal Stress Index (from Genova Diagnostics or similar) - it will provide you with a lot of information.