Reading problem, can't concentrate?

My whole life I've always been a avid reading, really articulate, could even read at college level in my early teens. But lately it seems like I can't read anything. I will read a sentence/paragraph over and over (even subtitles in a anime/game/movie) and it feels like it takes me forever to get past it. Other times I can read perfectly fine. Not sure what the cause could be; I've thought of confidence, not getting enough omega-3s/eating enough fish or maybe not reading enough lately. Does anyone know what it could be?