Thanks everybody...
It's strange how much I don't know about this disease, even after studying so much about it...
here's what's been going on:
my DD's wedding plans have probably stressed me out somewhat. I'm trying not to think about it too much...I'll be glad when it's over...
It was blasted hot all last week. It actually hit 100 one day. And I have been doing yard work, working out, walking the dog, etc. I was even sweating inside in the AC.
I helped DD and her fiance move their things into their new place last Saturday, and I felt so iccky I had to sit down. I kind of overdid it with the stairs, etc.
Last Sunday I washed the inside windows. Then I hit the wall. Slept most of that afternoon and Monday.
I was fatigued most of last week, and weak Sunday and Monday.
Today, I found out I have a UTI. It probably contributed to feeling crummy, because now I have a lot more energy.

I still don't understand how getting overheated or overdoing it can make you feel bad so many days afterwards...how do all of you deal with this? What I mean is, how do you monitor how active you are, or how warm you get? That's the part I don't understand yet. I am unsure how to monitor my activities so that I don't get into this situation.

Again, thanks for the info...I'll learn, I guess!