This might be ridiculously simple but it worked for me. I was exhausted all of the time and it was a combination of two things, first, asthma. I didn't have the typical symptoms. I am taking Singulair and it has made a world of difference.
Be sure to rule out allergies and asthma, they are much more common than chronic fatigue and can make you extremely exhausted b/c you aren't brining in enough oxygen to your cells.

Second, do some research on splenda and phenylalanine, the artificial sweeteners that are most typically used in diet pop and sugarfree food if you are a person that consumes them. The FDA says they are safe but I have firsthand experience and know numerous other women who quit consuming these sweeteners for a couple of weeks and felt so much better. I personally had joint aches, muscle aches, cotton mouth, gas, and an upset stomach. Within two days of quitting my consumption, I felt better.

Just a few cents worth - Cindy
PS - a wise doctor told me once to start with the most typical problems people experience and work your way out. great advice. (reminds me of Arnold Schwartzneger - It's not a tumor!)