It happens with Fibromyalgia. Also with Lyme Disease. I have one of the two and it is almost unberable to carry on a normal life! So I just change what used to be normal into a new Normal. I build my day around my rest time! If it hits out of the blue I just roll with it. This last week I had a spell and slept about 36 hours out of 48.
Hang in there!
Sundance(RB)