Does your body feel really heavy? For me, my muscles ache constantly, I feel like I've got no energy, and my arms and legs feel like they've turned to lead. My doctors don't know what it is, they suggested maybe it was something to do with the air I was breathing, like dust coming out of the heating vents. When was the last time you had your heating vents cleaned?
Another possibility is it might be something like chronic fatigue or fibromyalgia. If I remember correctly, fibromyalgia can be diagnosed by observing sleep patters, but chronic fatigue can't really be diagnosed at all. Really, I think when a doctor says "chronic fatigue" it's just another way of saying "i don't know what's gone wrong with you."