This sounds very similar to my situation. I haven't been diagnosed, but I feel that I suffer from dissociation without DID. The one thing that's helped me is a book that I'm working through by Suzette Boon called Coping with Trauma Related Dissociation. I haven't been able to find a therapist, so am using that. Like you I'm flooded with terror at various points throughout the day. I'll post my story tomorrow and hopefully you can identify.