sleeping all the time

I just slee all the time. I can do something productive for 10 minutes and I'll start dozing off. I have been sleeping around 18 hours a day for about a week, and the times that I'm awake I'm usually either eating, showering, doing homework, reading, excercising...yet they all seem to put me to sleep. Does anyone else have this? I just slept 22 hours straight and never heard my alarm clock and my roommate just turned it off because it went off for so long and she said she couldn't even wake me up. Wtf, fam.