Perhaps ask your doc about a blood test for your thyroid?...I spent almost 2 yrs wondering why I was suddenly so drained all the time. A specific test for thyroid deficiency nailed it. Now I take a replacement for the lowered thyroid hormone and feel much better.

Many people go undiagnosed with this Sass. Hyperthyroidism it's called. You may have heard of it already. The common symptoms are easy enough to find on the net. Best to see yr doc though. The fatigue for me was the main symptom AND the foggy brain...I'm much better now...still a bad day or two but nothing like it was.

In any case the doc needs a looksee. Please do this whether you like going to the docs or not. You'll be on the road to nailing this down and feeling better. I'm no doc but by god it sounds like thyroid stuff to me. Maybe someone else can comment as well.