Sorry about your headache,,,,I get affected by the sun sometimes. In the middle of the day I will get so PROFOUNDLY TIRED, and just have to go to bed for a couple hours, feeling so weak. It will just come on instantly out of nowhere when I am otherwise feeling well. Happens to my son also, and he says people at work just put their heads on their desk when this happens. I am pretty sure it is something atmospheric; I know some people are affected differently, perhaps headaches or nausea etc.
Hoping you feel better very soon....