To me it sounds as if you might have depression. I'm no expert though, I just have a few friends with depression and so have read a little about it (most effectively by playing a game called Depression Quest, actually!). It might be worth seeing a doctor about it if you think that could at all be a possibility.
I'm hesitant to give any further advice because of this. A lot of advice that ordinarily might be helpful just for burn-out might turn out to be unhelpful if you are actually depressed. (Although all the advice given by F'x looks fine as far as I can tell, except potentially you would have to be quite careful with what you chose to do for 3, as some options might make things worse.)