Many of the women in the trauma program I did took Prazosin for nightmares, with really good results. I didn't try it myself, but it may be something you want to talk to a pdoc about. It isn't a sleep aid, as far as I know.

Personally, my nightmares ebb and flow. If I am under a lot of stress or feeling vulnerable they get really bad. I do have periods where I dream well though. It's been several years of therapy for me.