Dreams a month after surgery?

Major surgery causes all kinds of stress on the body and the mind takes it all into account.  A small percentage of patients experience exactly what you are describing.  Another thing that could possibly be linked to your nightmares is Decadron.  Sometimes, the anesthesia provider or your surgeon gives Decadron (or similar corticosteroid) to minimize post-op nausea and help with post-op pain relief.  One of the side-effect of corticosteroids is vivid nightmares.  Ask your PS if that was given to you.  If so, don't worry.  The effects are short lived and will resolve over the next week or two.  

Sorry to hear about the distress these dreams are causing you. This is certainly not typical. Although there is no known link between surgery and the onset of vivid dreams, I am sure an argument can be made that overall stress (to which recovery from a major operation could certainly contribute) might lead to disruptions in normal sleep. I would not expect this to persist. It is not unreasonable to let your primary care provider know. Hope this helps and good luck with your continued recovery.