I couldn't hazard a guess about the Elavil. I'd go with your gut feel and your doctor's advice.
I haven't tried a TENS machine but I've read posts on the Fibrohugs board from others who have. Vaguely remember postive comments but no miracle cure, of course.
Hope you're feeling better. Good luck with the therapist. I couldn't do without mine. I would not be nearly as healthy physically or mentally, because when you're not feeling good mentally, it's impossible to get motivated to take care of yourself physically!