I had a little thing when young involving the aftermath of a fatal light aircraft crash in a starter job. Was complicated but I was involved with the recovery and the images threw me a bit of a curve. I mucked on (bad idea really). My talking to someone was several beers and a talk with a bloke who’d had similar and it sort of worked, but didn’t really. I was back in the saddle the day after, which wasn’t really the right thing. There’s more effective options.
Take some proper time off from work. You might suprise yourself and move on quite quickly. This is armchair psychology but I reckon it’s important not to use that time off to sit dwelling at home with all the thoughts circling around. I think that’s worse than even plodding on. Try and crack on with doing enjoyable things, any hobbies, walks, cinema whilst getting some help quickly as you’ll be back quicker and cracking on with life. Time is a healer as they say! You don’t have to go through your GP, you can pay yourself but it’s the cost. Maybe worth asking your employer if they have an occupational health policy that provides councilling for work related accidents and trauma.
It can be surprisingly effective to talk to someone professional. It’s not snake oil. Friends, family and trucknet are very limited value as people nod saguely but no one knows the mechanisms of how to explore helping someone with shock or a traumatic event. Speaking to a stranger who’s job it is, is night and day different. If the SAS have a charity for councilling through post traumatic stress then it’s good enough to take it that the method is worth while exploring if you’re really getting yourself in a pit.
Good luck!