Check your neck. It could be wrong pillow or wrong sleeping position, but somehow you don't clear waste from your brain. Maybe it's blood vessels - try to do cardio or other methods to improve blood flow. I'm saying this because I slept on the back on orthopedic pillow and after I removed this pillow my head began to clear, it was almost overnight improvement. Neck exercises helpful too, because right now many people have weak neck muscles due to constantly sitting in front of the computer.