Dreaming about your job every night , as anything else could be an underlying issue you have difficulty dealing with..perhaps you like your job and wish to do better, so you rehash it over in your head, a bit overwhelmed and can't let go.
Try before retiring at night, reading a very informative e-book titled.....
" Set your sleep on Auto-pilot " these are proven example studies. You may also want to check you vitamin/mineral levels through blood tests, via your physician.
Trust me these mean alot in the maintaining of a healthy immune system..
hope this gave a bit of insight to your question..very interesting by the way.