So, you developed symptoms and researched and chose the accident as the cause and PCS as the diagnosis. I don't think there is any evidence to link your symptoms to the accident.

The typical PCS symptoms can also be caused by many other issues.

My observation is you had a TIA or something similar and were struck hard with a 'What the ..... happened?" anxiety. With this anxiety, you became super sensitive to any sense of dizziness. Now, you maintain this super sensitivity to any dizziness.

I deal with 2 kinds of dizziness. The blood pressure kind that resolves when I give my BP a chance to catch up after getting up from a chair. The other dizziness manifests when I am overstimulated. I can usually overcome it by stopping to focus and catch my bearings. I can also get a sense of dizziness from thinking about dizziness. If I stop what I am doing to check to see if I am dizzy, I will notice some sensation of dizziness. If I ignore it, it goes away.

A similar situation happens with headaches. When somebody on NT complains about head aches, as I write a post, I will notice a head ache.

This is a known phenomenon sometimes called a memorized response. Thinking about a past condition can cause the symptoms of that condition to manifest. Therapy (CBT, Cognitive Behavioral Therapy) can help to break the memorized response.

A large part of balance is dependent on visual perception. Any visual problems can cause a sense of dizziness.

The tests you have already had likely cover any issues the Doppler will find other than imaging plaque that has formed in your arteries.