I am not a doctor, but when someone mentions brain fog my first suspect is coffee. At my first job right out of high school I drank a lot of coffee, and then I freaked out because I felt foggy. I had never really drunk coffee growing up, so the caffeine crashes made me think something was wrong.I def should look at IF (maybe one meal a day at night or 20:4) - they say that food is fuel but i don't feeling it. Every time i eat, no matter what i crash. It's better when i eat healthier but still happening. Generally i'm feeling a lot better after 6PM everyday. Like my brainfog is lifting a little bit and my head is lighter, hard to explain it. During the day i'm mentally fatigued even after 8 hour sleep and that's exacerbated after eating lunch. My mattress or pillow is a suspect because some mornings i am waking up with upper back pain and heavy feeling in the head. The other suspect is food and binging on porn.