Do you know if you snore by chance? I used to wake up with extreme fatigue and brain fog every morning no matter how much I slept. I didn't even know I was snoring and most likely not getting enough oxygen as I slept, until I my boyfriend told me that I snored almost every night. I really didn't know what to do because every search I did made me so paranoid for developing obstructive sleep apnea or even heart disease.
I started searching for and trying different things to help stop my snoring. A friend told me about one of the top selling anti-snoring mouthpieces, so I gave it a try. My boyfriend told me that he didn't hear me snore at all and I was starting to wake up feeling rested.
My main point is, you never know if there's something else you're doing that could be contributing to your chronic fatigue.