I don't believe dyslexia is a born disorder, and can be developed at any stage of life, given the circumstances leading to the development. It doesn't occur out of the blue, there is always a reason for the development of a learning disorder. I would not jump to the conclusion that you have dyslexia, though. It is simply a possibility. Other reasons your reading and writing could be affected includes lack of sleep, hormone rampages, environmental changes, etc. etc.