Background Music

I have background music in my head but it isn't music. It is a constant replay of things I have done wrong. Things I should have handled better. Worries about how other's see me. It is always there. I have nightmares every night that I only remember for a few seconds after they wake me.
I still haven't adjusted to my new work area/situation. I feel I don't fit in. I'm conflicted. I'm guarded. I feel threatened. I hate going to work now.
I am tired all of the time.