When you wake up from nightmare (should be occasionally)

Do you breath heavily? Sweat heavily? Do your hands shake? Does white "screen" flashes in front of your eyes? Does your heart pound? If so, then PTSD is a possibility.

If not, it's a part of your psychosis. Again, to be diagnosed with PTSD, from PsychCentral's own website (the criteria given there is approved internationally) you must have been exposed to a serious injury to be classified to have PTSD.