So I was having the same problem, everything was very grainy looking and pixelated. When I would pop a pain killer it got way worse. None of the forums supplied a fix. Everyone said change your sharpness... Still had an issue, until I started checking my Nvidia GeForce Experience settings. I had a setting turned on that changed my image scaling in game and had never realized it caused my game to look pixelated. I turned this setting off and everything in game changed and I no longer have a pixelated picture.
How to How I fixed it:
1.) Open Nvidia GeForce Experience.
2.) In the top right corner click the settings icon.
3.) Scroll down to the area called "Image Scaling."
4.) Make sure this box in not turned on.
I hope this fixes any similar issues others might be experiencing.