Hi ChevyGurl,
Welcome to the CFS board. I moderate here also!
Amitryptaline (sp?) is an antidepressant, and a type known as "tri-cyclics". Tri-cyclic refers to something about the chemistry of the drug. Sleepiness is a side effect of all tri-cyclics, and amitryp. is considered to be stronger than others, in regard to sleepiness. So it's NOT technically a sleep aid. (I really HATE it when Drs pull tricks like this--but I'll try to restrain myself and finish answering your ?) Often antidepressants ease the symptoms of FMS, but Drs often prescribe them for patients who make any report of achiness, whether they diagnose FMS or not. So from the Dr's point of view.... You know...I'm just going to leave it at that. I can't finish without getting on my soapbox about this. Just know that it's not technically a sleep aid, and that, as an antidepressant, it MIGHT ease some achiness and other FMS symptoms, including depression. Also, personally, I can't tolerate it (My body doesn't tolerate it, as a medication. Not tolerating some Drs' behavior is another matter!!). 
Take care.