What Causes High Sensitivity To Heat?

I am hot all the time! Not hot flashes, I went through those. Our house is set at 65 in the winter and I am in shorts and a t shirt, I sleep with the window at the bottom of my bed wide open, out temps have been -20 degrees for weeks. I sleep in a thirt and shorts, and also have a ceiling fan running constantly. I a 62 yr old female. We went to the mall to walk today. I wore a light weight sweater, it s 10 degrees out. Left my coat in the car and after an hour walk I was sweating enough for the hair at the nape of my neck to be wet, and sweat running down my face. I dread any temps over 65 degrees. This is a constant feeling.