Grace, when I was a JW Pioneer, I worked full-time and pioneered. When I married I was no longer a pioneer and continued to work full time!
I have been diagnosed with chronic fatigue......years after I left "the truth"......I'm symptom free with the exception of times where I'm not getting enough rest, improper diet and/or I'm stress or depressed! It is complete and utter exhaustion along with body and muscle aches. Sounds a bit like life in general.
I think sometimes there are JW's who have been medically diagnosed with it and when they tell others about it, the others self diagnose.