I know EXACTLY how that feels because that is how I'm feeling now! But I am sick, I have a cold, and I have also been working major over time. So I'm sure that all ties in.
exercising! I haven't been simply for one fact: I can't breathe!!!!!!!! lol.
But I agree with Jay, if you keep feeling that way, maybe talk with your dr about it. Also I know that SAD (Seasonal Affective Disorder) is pretty common this time of year too. So maybe get out in the sunlight (if you have any).