Hard to say what would happen in the car accident. But do you stutter when no one is around? Try reading out loud or talking to yourself and repeating sentences that you stuttered on when people were around. Personally, I'm perfectly fluent when no one is around. I'm 27, have stuttered since I was 7, and never noticed this until this year (I started living alone). So it seems obvious to me that it is psychological. Now, if I pay close attention, I can even feel my throat clench up as soon as I walk outside or whenever my phone rings.