Too much blood in my caffeine stream

I'm feeling somewhat out of it today; in fact, very much in the way that I feel when my major source of energy/awakeness is caffeine. I'm not actually clear why this is; I haven't been sleeping less than usual, or eating differently, or drinking more caffeinated beverages. There's a little more stress -- still figuring out this SO-has-a-job thing, have a big lab due Thursday that I've barely started, strange uncertainties at work -- but I wouldn't think that'd have this kind of effect. Night night.