I forgot to mention that I've had no caffeine in 6 days now. It started semi-accidentally: last Wednesday, when I went to take my caffeine pill in the morning, I started retching, so I spit it out and skipped it entirely. After that I kept it up since I figured I might as well try it. At this point I think I can say that caffeine was not responsible for my evening sleepiness (I feel as tired now as I always do at this time on a workday), but also that it wasn't doing much for me, as I feel pretty much the same during the day as I did before. Also, caffeine wasn't really helping me get up, because I didn't take it until I was already up anyway.