I could of written this myself - minus the car accident and health anxiety. Mine too started off with a couple of panic attacks which escalated into generalized anxiety. Mine didn't start until i was 34, which was 6 years ago and it just came out of nowhere. I think the driving anxiety comes as par of the course with panic disorder/agoraphobia, but i can imagine going through what you did, the fear seems more real, rather than just your anxiety talking, so to speak. With me, the issue is being trapped in traffic, or having to drive further from home or a safe place than i feel comfortable with.
I'm not sure whether you have looked into CBT therapy but it did help me a lot a few years back. It's hard work, but the more work you put into it, the more you will get out of it. My anxiety had been manageable for quite a while, and stopped dictating my life to a certain degree, although it never totally left, but i've been under quite a bit of stress for a couple of months now and its back in full force again.
If you are totally housebound, start trying to take baby steps like even walking outside into your garden. With the car, go out and sit in it for as long as you feel comfortable with, and do it the day after, and the day after that..and so on. If you're anything like me, you want a quick fix and want to be better like NOW, but it wont work that way, although i am sure you don't need me to tell you that. My logic was, I'm anxious at home, I'm anxious if i go out. So, do i lie down and give in, or do i try and claim my life back?
The key, i think, is exposure and distraction. Do you have hobbies to take your mind off anxiety? Keeping busy helps a lot. The more you entertain it, the worse it seems to get, and the longer it hangs around.
Anyway, i've rambled on enough. Just wanted you to know that you're not going through this on your own, and it CAN get better.