Having Nightmares Every Night?

I can honestly say that my entire life I have never had one good dream. Ever since I can remember I have had nightmares or some form or type of bad dream all involving shootings, murders and kidnapping most of which is happening to myself. As far as I'm aware I have never been in any sort of extreme traumatic situation before. I am just curious about some possiblities as to why this keeps occurring or if anyone has ever has a similar experience before?