Hmm perhaps there lies the problem. There are flashback like nightmares that are related to the trauma itself and then there are the 'ptsd nightmares' that are not so much related to the trauma. It could be that you need to lower your anxieties so that you can sleep better. It can be done with anti anxiety medication of course but you can also try to strive for the things in everyday life that boost your self esteem. The coping skills taught in therapy can also help us find meaning in our lives where everything seems chaotic. So reading, hobby related stuff, pushing yourself to do things when you would rather avoid out of fear, chores, a lax job and a schedule to go by along with a journal or diary, even keeping up with a planner.
If there are missing chunks of time from the events of your trauma try something I did. Go through the events leading up or as far as you can go, if you can go all the way. I should warn you that this exercise will cause you anxiety. You must try to remember how you felt not just what you were doing as you go, the events written out in linear fashion, example ("I didn't want to face what was happening to me because" or "I felt that if I went to ask for help, it would mean that this really is health related and I could be facing death soon".) The idea is that you think about the events as they unfold while remembering anything you were feeling or thinking. As long as you go slow and think about it, you will begin to write down the missing moments, feelings and details. If it works right, you will be shocked to find that you are writing down memories that were displaced by your own emotions, hidden under a cloud of nervous system responses designed to keep you alive on the most basic and fundamental levels.
It is of course very triggering but the release that is felt should be ... well it could very likely lead to a breakthrough. I couldn't say that it would be a guarantee to work but if you put the effort into it, I do not see why it wouldn't help. Afterwards you will probably feel both weak but also bold in your afterthoughts. It is a good idea to have somebody who understands you to talk to and get encouragement from and comfort soon after you have written down your story, felt it and then internalized it.
You might have already told your story in therapy and been emotional about it even but it is not the same as writing it, because you have to really remember and feel the things that your own mind locked away. At some point, soon after or after some thought, can we understand what happened? I don't know but on some level, things will start to be 'filed' in your memories the way they should be, a memory..yes a bad one and bad feelings that might challenge your fears. Fears that were faced though, and no longer a monster locked away within the dark recesses of your mind. We have to tell ourselves that we are okay now and understand in some way that we are still alive and can grow now after facing it in this way I guess.
There are other dreams that are seemingly unrelated to our traumas and more an effect of having ptsd. Many of us have had cycles of insomnia followed by bizarre and very vivid dream like nightmares. They don't always scare us like we would expect. If you could imagine seeing grotesque wounds on yourself after falling off a cliff. The dreams are real enough that you are actually surprised that you are still alive yet there is never a lot of fear or emotion behind it, you just get up and walk away on your crippled limbs. In my case the dreams are seldom violent in any way but more twisted and morbid, involving accidents and witnessing things that should terrify due to its vividness but it doesn't for some reason. It does however effect you in your awakened state, anxiety might start to build as you wake up and remember the dream and can become and intrusive thought that gnaws at you for a few hours. These phases can last months or weeks and come back again as your sleep habits change. One thing most of us that have experienced this that I talk to; "Prazosin is the only thing that keeps these dreams from happening".
I honestly don't know how effective the Prazosin is for nightmares related to the trauma, it could be that the trauma hasn't been dealt with in your mind as well as it should be yet. I do know that the drug works by blocking signals that pump adrenaline into your body or something to that effect. If the trauma still poisons you so, I don't think that the Prazosin is going to be your answer. It is just like you said, "I am still having these nightmares even while on Prazosin". Granted, it probably is helping a little by blocking the adrenaline but I just think that it wouldn't prevent the memories from surfacing in your sleep. It does however have a profound effect on these unexplained ptsd nightmares that make no sense and seem to be centered around nothing. I hope doctors don't think that this is some kind of miracle drug they can just give to anybody who has ptsd as some sort of miracle treatment, we all still need therapy and need to make the steps to unravel the issues that made us the way we are.
