The alarm finally did go off and I got up, took some headache meds and got G to the school bus. Then I went back to bed and slept until 11. This was odd because I've been getting tons of sleep and have been feeling well rested. When I woke up, I felt fine.
I might have gotten the headache because I only had a third of a cup of coffee yesterday morning. I thought of having some coffee last night to stave off a caffeine withdrawal headache, but I didn't want to stay up all night so I figured I'd see what happened instead. Next time I have very little coffee in the morning, I'll try to remember to have a cup in the afternoon to make up for it.