Why not try pregnenolone, the grandmother steroid adrenal hormone, instead? The body makes DHEA from preg.
With CFS/ME you'd probably benefit from the extra preg; however, your body might not be making all of the conversions at a normal rate to allow you to make enough hormones at the end of the production lines, for example cortisol. http://en.wikipedia.org/wiki/File:Steroidogenesis.svg
Note DHEA is not abbreviated in the image.
Have you gotten a good hormone panel? It seems fairly common for people in heavy metal detox groups to report that they don't tolerate normal doses of DHEA. They don't seem to convert it towards Testosterone at a normal rate, maybe due to weak sulfation that seems to be common with a HM problem. Note Chronic-Fatigue-Syndrome is also quite common in detox groups since adrenal related systems are so vulnerable to HMs.
I've found a nice combo for myself. 10mg preg x 3 daily plus 6mg DHEA once or twice per week. I like the feeling of the extra DHEA. Recent followup hormone tests suggest that I've gotten a good feel for what my body needs.
Originally my doctor suggested 25mg DHEA after testing. It never felt right. I took around 12mg almost daily with nice results for maybe a year.
When I started HM detox--Cutler--I increased my zinc intake. For whatever reason I started getting symptoms of high DHEA and T, including deeper voice, grumpy old man personality, even heart palpitations. That is when I started to cut back and change over to mostly preg.