Have you had a fright, this does happen or else have you just got scared of going out in your car. You can go out with a driving instructor to go over some points that you may be doubtful about or else get a friend to drive with you, gradually taking on more challenges. The other way is to just take the car out when there is little traffic and gradually go from there. There is also professional help out there too if it is a phobia. Whatever is the matter it is nothing to be ashamed of.