Anecdotally, but the missus experienced the same. Fatigue, brain fog. Oh you're just bored said the doctor. Blood turned out fine. This lasted for about 3 year

Anecdotally, but the missus experienced the same. Fatigue, brain fog. Oh you're just bored said the doctor. Blood turned out fine. This lasted for about 3 years (short, when I read other people's experiences here). We moved, and got a new PCP. The missus brought up her fatigue again and lo and behold, through a series of tests and referrals, all initiated by the new PCP, the ended up being diagnosed with Ehlers Danlos Syndrome. Does that change that she feels tired? No, but at least it gives a reason and that does help in allowing yourself the liberty of taking it slower for a day.