I have extreme heat sensitivity as well as the sun. My dr thinks that mine is due to an underactive thyroid. But even though i've been taking synthroid to correct the problem, I still am extremely heat sensitive. Their are sometimes when I cant bare to take a shower because even the hot or warm team from it about puts me down. If i'm in a building that is warm its the sam thing, i immediatly get uncomfortable and a little woozie. Also, the sun is killing me these days, i run to the car with a towel draped over my head, and block the sun with it the whole time im in the car. I cant figure it out either...but I feel ya sister...its terrible isnt it.