I recently saw a head on collision where several people burned to death....?

i was a volunteer fireman, and after this i found it hard to eat. I try hanging out with my friends but i start getting small panic attacks. I feel nauseated 24/7. I found lately when i have company i tend to lock myself in my room so i can be alone. I had nightmares for a while after the accident but i dont have them as much.. what is wrong with me?