You having a hard time with anything or bored; could be related to something going on in your life. If you're working hard in therapy or anything, I use to have a hard session, not particularly bad, and practically fall asleep in my dinner, would be in bed and sound asleep by 8:30 that night, etc. If you're mentally working hard on anything that could be wearing you out. I'd go see your doctor, get a quick checkup to make sure there's nothing physically wrong; sleepiness can be caused by lots of different physical problems that don't present much else/that you wouldn't suspect, etc.