Why do I have trouble reading musical notes, is there some sort of psychology behind it?

I have been playing the piano for about 10 years now. The funny thing is though I still have trouble reading notes. I will take a piece of music and start to play it, but I will hesitate for a long time. I feel stupid because with the amount of time I've been playing, the notes should just automatically pop into my head. My teacher has even gotten on to me about this. I don't know whats wrong with me. I wish I could pick up a piece of music, glance, and play it automatically. Why can't I do this? Is it some type of dyslexia or something wrong with my brain? Any type of science behind it?