Sleep, where did you go?

So for the past three days, I've been waking up at 4:30 in the morning. Never can get back to sleep. I was a grouchy, beastly teacher yesterday. I blame it on lack of sleep. Now it's Saturday and I was really looking forward to sleeping in. Except that it's 6:30 in the morning and I've been up for over an hour. What the heck is wrong with me?!?!