I don't think traumatic stress has to show up just in nightmares. Depending on the type of stress, flinching when someone touches you or moves suddenly (my favorite was flinching when someone near me raised their hand; I thought they were going to hit me) or avoiding certain innoculous-looking situations or places. I get extremely anxious and have difficulty sitting on a picnic bench because one went over and trapped my husband and me underneath several summers ago. Any extreme anxiety or "stress," fight or flight quality, may be an indication of PTSD. If you dwell too much/too often on your trauma, can't get it out of your head, that qualifies too.

It may be that you just don't remember your dreams well? You could have bad dreams and not remember them. We all dream something like 5-7 times a night but I don't remember more than 2-3 at most and that's only some nights, maybe I'll remember a dream or dreams twice a week. Not a very good average and I like dreams.