Can't Understand Why

So over the last few weeks, I've been utterly exhausted. I can't muster up the energy to do much of anything and am finding that all I want to do is sleep. I don't have a single clue why I'm so exhausted. It's not because I'm up ALL night, usually if that happens and I get even 3hrs of sleep, I'm not so tired, but this time, I'm wiped out. I think if this persists, I'm gonna call my doctor and see if she knows what would cause this much exhaustion.