Thank you for the reply, Mark. I believe my incident last year was more a case of whiplash as my neck was noticeably more sore/stiff. I don't recall hitting my head with that fall.
Since anxiety can mimic symptoms, I can understand why I might be feeling the way I do, but I'm surprised that the effects of anxiety could really be that powerful.

I do admit that I struggle with health anxiety, and this can sometimes have me overreacting to events like this. When I got over the anxiety of my fall last year, I had a great summer and things were normal,
so maybe my current anxiety of this accidental bump is also giving me symptoms. I know its about 60-90 Gs to cause a concussion injury, and I hope my head impact on the car was a lot less than that.

It will take some time before I can settle myself and remove my feelings from the bump and the effects from my concussion anxiety. Since I was back to normal after my accidents, I think I should recover from this as well,
even if there is a part of me that doesn't believe that yet. The headache I received from the bump lasted only 2 days and I currently have light pressure and feel off, which could really be just anxiety;
my main worry is whether or not bumping that car was a great enough force to be 60-90 Gs, and be concussive.

I think if was not concerned about bumps & concussions, I would have accepted and ignored the bump without a second thought.
I do think I've made progress in overcoming my anxiety, but incidents like this bring me back to a fearful place.