When I want to stress it, I call my fatigue "exhaustion" I have been known to call my heat issues "heat exhaustion" as well.

I do like the "intolerant" word because folks understand what it means.

I find that most folks are so busy trying to tell me about their own troubles that they are not really listening when I speak about mine, unless they themselves have been truly ill and completely get it when you say "im wiped out!" Others will say "omg, me too! you can believe what happened today" those who have been truly sick will say "I agree, I can see you are struggling today."