As I noticed, after reading 2-8 thousand words a day, after a few days of reading like this, it becomes very difficult for me to read, and I started reading actively lately, before that I only watched TV shows and movies, and now I have a slight headache, the text is floating, I even confuse words. In fact, that’s why I used to read very little, and now I’m so tired of TV shows and movies that I’m willing to force myself to read, even if I have a headache, to become emotionally attached to books instead of just consuming like zombie like I used to.
If you wear glasses or contacts that are for seeing at a distance, it’s hard for your eyes to focus close-up for very long. Same for if you don’t wear glasses at all, if you are reading a lot. So depending on your situation you may just need to take your glasses off while reading, or pick up some cheap reading glasses at the drugstore–making sure to get the right type for easily focusing on the page, or even get bifocals. Best bet is to get an eye exam and tell the optometrist what you’ve said here, so they can figure out what your best options are.