Would be well worth having your iron levels checked - a very common cause of letharg, general tiredness.
Just had mine done, and after six months of barely making it through day, not exercising for lack of energy and struggling horribly to get out of bed in mornings - iron tablets and a few steaks a week have done bloody wonders!
Hopefully it isnt anything but not sleeping well. But you should have blood work done for your thyroid. fiberomyalgia they dont test the blood for it. Both are miss diagnosed. Both cause exesive tiredness, weakness and depression. And yes your iron.
I just read that fibermialgia caused finger nails to have ridges.
There is a possibility it could be Fibromyalgia, also. I would look it up & see if you have any of the other symptoms. Many of the symptoms can be for other disorders/syndromes, also, so it often goes misdiagnosed, or even undiagnosed altogether. All over weakness & constant tiredness are often the main symptoms of Fibromyalgia, along w/ unexplained muscle soreness. Most often, the tiredness has been ongoing, but has been 'explained away'- oh, I didn't go too bed early enough, I did too much today, etc. But definitely look it up & talk to your doctor about it.
I think you should watch a laughter show or program that can make you laugh very hard, which eventually release the antidepressent hormones and yeah it will also raise your iron level.......!!!
As soon as I saw the question I thought blood and iron deficiency as most of the others have already said. Its usually nothing serious but best to get it checked out and your doc could suggest something as simple as a temp change of diet. Depression does have an effect on sleep patterns but if theres no specific reason for being depressed it could be caused by this sleep thing. Even when you are tired if you exercise you go to sleep with a different kind of tiredness and so usually have a better nights sleep