There is one thing you can try. It's called lucid dreaming.If you realize your dreaming you can control what happens. There are a lot of web site that can teach you how to do it.
It can help you to concur your fear and it can be fun. Think Neo in the Matrix.
This works! This is how I rid myself of several recurring dreams from childhood. However, as far as I know, it doesn't help you deal with the actual issues you need to face, so be aware that you have some other work to do to overcome your challenges as well. All the best to you!
Try seeing a therapist
Dream catchers work well
What's the nightmare about?
Teach yourself to lucid dream. Or play peaceful music throughout the night. Lucid dreaming takes time, but when you're able to achieve it, you can do some pretty awesome stuff... like control your dreams. Kill Jason and Saw.
Best way to lucid dream is to keep a dream journal. As soon as you wake up, write down in as much detail possible what your dream was about.