I have severe fatigue as well. I could only work 22 hrs per week because of it. After much research, many blood tests and a sleep study with no answers and 4 years later I found a syndrome called POTS online. Postural Orthostatic Tachycardia Syndrome. When people with POTS are acctive or even just stand, the blood vessels in their pelvis dont constrixt as well as people without POTS, their blood rushes to their feet and legs more than normal and it causes fatigue, concentration problems, dizziness and fainting. I would be driving and have to pull over because I was so sleepy, usually in the early afternoon. I found a good Neurologist who specialized in the syndrome and had a tilt table test done. They strap you to a table and moniter your heart rate and blood pressure while laying down and then standing up. If your heart rate goes up more than 30 beats per minute when you stand, POTS is diagnosed. Before I went called the Doc, I took my own pulse while lying down and then while standing up, each for a minute. It went up more than 30 beats per minute. The only treatment they offer is LOTS of gatorade or vitamin water, anyrhing with electrolytes, increase salt intake- add extra to your food or there are capsules and if it's bad enough they may put you on a low dose steroid. I wish you luck as I know this can be so frustrating!!!! Let us know how your appointment goes