Do you have a reading center at your school? They might have tests and ideas how to help get you out of the habit or help you if you have a problem. I have some problems because my mother was aphasic ("Partial or total loss of the ability to articulate ideas or comprehend spoken or written language, resulting from damage to the brain.")
when I was learning to talk. I just ordered my lunch wrong a couple hours ago :-) I normally have my hot dog with ketchup, mustard and onion and received one with tomato, ketchup, and onion! Confirms my poor husband's trials and tribulations with me sometimes because I come up with wrong words. Do you have more trouble than usual when you're tired or worried?