People can dissociate without it being a disorder, I'm wondering if that's what you mean. In a traumatic experience, often the person will dissociate and not remember parts of the event. However, this is usually in response to a perceived threat at the time. You wouldn't dissociate beforehand, it would be a reaction to the event.
Are you thinking something has happened, or are you worried about something happening? If you're worried about something happening, that is something to work through with whoever you're seeing for the ptsd. If something has happened, perhaps a little more context might help out...