Well, I can only give a unprofessional opinion.I recall you saying you are an alter in your system.... do you have 'dreams/nightmares' of others? I know this is the case with another alter I know in someone elses system but he also has the role of an internal therapist too.
For me- I feel that when I have nightmares that cause a lot of physiological arousal when I wake up.. I tend to feel it's connected more to my trauma issues even if not a direct memory because it seem's that 'regular nightmares' are kinda like... oh that was scary for one second ut as soon as you wake up and know it wasnt reality, it seems like it's no big deal to the body. I dont feel truly fearful, afraid as I might feel from another type of nightmare (memory type.. even if abstract).
Than again.. I always take most dreams/nightmares with a big grain of salt because our minds are influenced by so many many things. Life worries, stressors, pain, meds, etc.... and just the creativeness of the temperol lobe! haha.
One thing I do is that I write down my dreams if they bother me enough. i write all i recall from the dream and than will add my notes, connections.. intepretations of it.
I have shared a couple dreams with my therapist and it has always been quite insightful and enlightening especialy to how they relate to my struggles at the time.. transitions... etc... I know this isnt that clear but Im really medicated for pain heavily and it's hard to think.
Those are my thoughts fo rnow