Ozzy/Horse...
reading this has really shocked me and my sympathy to the both of you. before i read this i kind of assumed you get out of a car accident in one piece you're all good but obviously not.
i wrote off my astra in 2003. 45mph straight in to a tree. luckily i didn't have any injuries or any problems at all. apart from ''the worst'' which doesn't bear thinking about i got out of it with one small cut. but sounds like much worse is a very real possibility and most shocking is stuff i never even considered like cronic migraines 
I think age plays a part...
...as a teenager, I was given a little yellow van and £1m of liability insurance. Well, you can guess the rest

. Yes, they (mostly) all hurt at the time, but after a couple of days, all good.
Then just over a year ago, I had that potentially serious one, involving 4 cars, including the one that t-boned me, and a central reservation. The next day, just a bit (err, lot!) of concussion, but no aches and pains... ...until that evening. Jesus wept did it hurt.
Took ages to register with the local quacks (only lived here 12yrs), tthen ages to get an appt, only to find the NHS were their usual, useless, helpless selves, hence why I hadn't bothered to register.
I had to go down the insurance route (and what an eye opener that is - nobody cares about your health, only about their cut, and the whole industry is in on it) to get private care (which, apart from the physio, is all 'dangle berries' - my "doctor" rents out a conference room in the Holiday Inn to see patients).
13 months later, it still bloody hurts. But as all the scans have come back clear, so its all muscular/soft tissue which should sort itself, I took myself into a corner, and had a quiet word with myself, along the lines of "its only pain, be a man". I normally refuse medication, although some days I have to relent

As time goes on, I have more and more pyschological issues with the accident itself, which I thought I should be over by now. Possibly a realisation it was a far more serious accident than I gave it credit for at the time.
Related, it has also caused other issues, which are probably around weight gain, through a year of being not very active. I was a fatty before, but now....