I've Started Having A Serious Issue With Heat Intolerance. Even

I've started having a serious issue with heat intolerance. Even a slightly warming temperature bothers me (like mid 60s up), I get extremely sweaty and red, no matter how much or how little exercise I get, feel disoriented whenever I move, and get a heavy pressure on my chest that makes it hard to breathe. I don't know what's going on and it's really bothering me. I can't be stuck in the house with an ice pack every slightly warm day! What could be going on there?