That actually sounds very similar to me most of the time. Up until say 5 pm each day I am so tired I could go to sleep at a moment's notice, after that though, I'm wide awake and I have to make myself go to sleep at a decent time (usually around 11, because I have to be up at 6). Sometimes I actually fall asleep, sometimes I just lay there forever, sometimes I just get back up, or not go to bed at all. I think for me its an anxiety thing and a sleep schedule thing. For some reason, I am ALWAYS more tired during the day (unless I am hypomanic). Depression or not, though, I am tired-tired during the day.

Oh, and I do most of the time, feel my anxiety. A general tension in my shoulders, my stomach is in knots, etc. My anxiety is related to my paranoia and I, for some reason, am less paranoid at night time. Hm, so maybe that's why its easier for me to be awake then? Because for me sleep definitely = safety.