You don't say, but I bet you never had these feelings before the accident?
If not, the first thing I would suggest is a series of counseling sessions to talk about the trauma you experienced. In my opinion, (and I've never been a mother) the trauma was greatly increased because your baby was at risk as well. I honestly feel this kind of experience is very much like what so many of our soldiers come back with - Post Traumatic Stress Disorder.
Sometimes it takes a good while to really "get it out" in counseling, but I do believe it will help you a lot - obviously you can't go through life feeliing like this in any case. Facing it is your only option, and a good therapist can make this a much easier and more productive process.
I wish you the best of luck in this, but reaching out to this Forum is a great first start.
Best in Health
ThyroidHunter
Also, even if you were not the driver when the accident occured, it no doubt made you much more hyper-sensitive to driving a vehicle yourself. That has led to increased anxiety and panic just being on the roads.
Many people feel tense when they're a passenger in a vehicle because you don't feel 'you are in control'. Having been in that accident and knowing you were pregnant is what probably caused your feelings of 'not being in control' to reach this level of panic attacks. One way might be to talk these feelings out with your family and friends so they know to be vigilant about their driving with you as a passenger. Actually anyone who drives should do it in that manner. You could also seek therapy to discuss it.