I agree with a previous poster OP, get yourself to your doctor a.s.a.p. preferably not the one you saw before, who was obviously a real misery guts, as so many people call them 'happy pill's, simply because they make you feel happy again, when you've been miserable.
I have been on anti depressants for two thirds of my life, they just keep me on an even keel, but even if I'm weaned off of them slowly, after a few months I go downhill. So please don't be scared to take them. They will, I'm sure, make you feel much better, and more able to cope with your fears about your DS being a new driver.
I think at this stage with his driving, I would be asking him not to take more than one friend out in his car with him, and ideally only to drive alone. However, the fact is, we can't wrap our kids in cotton wool, we have to let them learn to take care of themselves, and I feel sure that with some anti depressants you will find this much easier, and not worry so much.