Is this PTSD? What's wrong with me?

It could be a post-traumatic response, but it's not PTSD. PTSD only occurs after a person has lived through a traumatic incident in which their own life has been threatened or in which another person has literally died. This is actually a fairly normal reaction you are having and it will get better with time. Just be patient and try to distance your mind from the incident. Lingering on thoughts of it will only make matters worse. Good luck.