Did you have any Traumatic Brain Damage in the accident? It sounds like that accident had more effect on you than anyone is willing to accept.
I know for me, my migraines made my depression so much worse....they ended up being 24/7...couldn't handle noise, smells, or sight....even closing my eyes hurt. Luckily, I'm on pain medication for my migraines which are continuous without them & have complete relief.
Sounds like you need some medical testing to check out what is causing you your problems......many times physical problems can show up as mental. I am sure you had some problems prior to the accident.....but with the accident making things worse, maybe there is something they can help you with physically that can help you mentally.
God has his purpose for us here in the lives we touch as examples. It's always best to go Home on God's terms & not our own.
Be nice to yourself & show yourself patience & know that you are cared about