I'm sorry you're struggling with nightmares: trauma work is so difficult. Perhaps he might have some strategies for you, probably useful to spend some session time before delving too deep on coping strategies too- I find trauma work very agitating personally.

My therapist recommended a story by Clarissa Pinkola Estes when I was scared of intrusive thoughts and nightmares related to trauma work. (Amazon.com: The Sleeping Beauty: PhD Clarissa Pinkola Estes: MP3 Downloads) I also created a playlist of soothing, light sleeping songs that helped a lot. "Knock out tea" is another cheap, soothing part of my bedtime routine when I feel extra nervous.