I use to do it all the time as a kid because I am prone to losing things like bookmarks. Now I just track the page I'm one through Goodreads, or in the case of my kindle it's already saved.

Having to reread entire lines is what led me to being diagnosed with ADHD. Check vision like other guy mentioned. It sometimes helps for me to listen to the audiobook version while reading the print in order to retain focus, especially for longer texts.

I use audiobooks to help me concentrate on reading books I didn't particularly care about. I listen while reading alongside text because I hate rewinding. It keeps me from browsing the internet or getting distracted with something else.