That could be why.. Some people dream of memories..... Some people may just have an overactive imagination.. while others are dead set in knowing without a doubt that something in their life has been experienced before but can't remember it ever happening in this life... I'm not an expert in this sort of thing, but I do know it's possible..
For I know there were things in my life growing up that I knew way too much about and no one ever mentioned it. Most of the time I would get a "sit down and chat" and they would ask me where I heard it from, and who told me that and such when it was just something that came from blind knowledge (only way i know how to explain it, as it was knowledge, but I had no source to credit what I knew to).
I also would trace a sideways 8 all the time from a really early age, my parents got mad at me a lot for this.. I remeber when i was 2yr getting in so much trouble because i blew on the window and did it there and left a mark..
And had other things like memories that no one can explain to me.. and now that i'm older they are not as clear as they once were but i know they are not from this time period...

I'm sorry you're having such tramatic dreams.