Meowrie,
I have had for sometime what you describe.
It sounds to me like your nightmare can be PCS, or PTSD.
I'd get the most horrible and realistic nightmares!
My TBI cause me to have sleep apnea.
My CPap machine, (and, my doctor and I have added oxygen) has been a great help.
But, you may really need a clinical or neuropsychologist.
If you have the coverage, or ability to pay, go for it.
Discuss it with your doctor/ neurologist.

Any accident like you had, will bring a huge amount of stress.
And, that brings on PTSD.

I hope this tidbit may have helped.
Feel free to PM me.
I've been over ten years with the TBI.

(It's getting better all the time)....

Be well,

ASB
Pete