I take seroquel and I have PTSD so I can't blame the seroquel for my nightmares. In fact the p doc who prescribed the seroquel for sleep is the one who diagnosed me with c-PTSD .
I've also tried : trazadone, ambien, sonata, lunesta, gabapentin , valerian, melatonin. I always come back to seroquel. It's the only thing that puts me in a deep sleep. Have you tried prayer or meditation or exercise during the day? Are you taking anything else?