I too suffer from PTSD and struggled with sleep for a long time. After trying many different medications and strictly following sleep hygiene practices I finally asked my GP for a sleep study. When I did sleep I had very graphic dreams even though my sleep study showed I had sleep apnea and only made it to the 2nd of the 5 sleep stages.
I started using a CPAP and a new medication, both of which helped me sleep better, but did nothing for my dreams. The only thing that has helped with the dreams is therapy. I will still have dreams but they are not every night.