Ginny, I just tried taking 50,000 units of Vit D weekly to improve my level for the second time. Once again, it made me feel terrible, causing additional muscle pain, fatigue, flare etc. My rheumy told me 4% of people have that response - and so they generally never see it, but it isn't unheard of. Lovely being unique, eh?
Glad the puzzle seems to be solved for you!