I am seeing things

Not being funny, but I just thought someone should know if this is some last stop before complete insanity, but I am now seeing things when I read. As I read something and my eyes inadvertently skim ahead, I will read things that I expect to see in later sentences. I then get to those later sentences and they are not there. It happens a few (5-7) times a week now, for the past month or so.