since I was a child I have gotten sick (feeling extremely exhausted and headache ) when I am in the sun for long. My sister is the same way. This has gotten worse every year since and at this point if I stand outside in the sun when it is hot outside for about 10-15 minutes it will happen. It happens faster and the result lasts longer every year it seems. I used to get better after sleeping but now I still feel very drained the next day as well. No one has taken me seriously about this. Do you have any idea what might cause it?