Your S8 uses an OLED display, I am guessing everything else that causes you problems is LCD.
Some of my screen problems are linked to food. I am fine today, but if I were to eat something containing cooking oil I would not be able to use my monitors without pain for about 5 days. Unfortunately, eating cooking oil causes me no other problems, I only discovered it was the cause of my worsening screen problems by dumb luck. My problem with cooking oil started suddenly, I was fine ok day and in pain the next. Funnily enough, when it started I could use my OLED Samsung S3 mini without pain, it was only LCDs that gave me pain.
Its a long shot, but try eating nothing but plain pasta for a few days and see if you get better. If you do, you can start looking for what your problems foods are. If it doesn't get better then you'll know its not a food thing - or its the pasta!