I don't have any wise words, just a message to let you know that; no you are not alone.

I had an alter like that. My integration was rather rough and I live in fear that it will all fall apart, and that will happen again. I'm realizing that my best bet is to work with my current T and be open with her about my past. If I try to deny my fears then they are in control. So please be sure to tell your new T that you/they need to work on a plan to keep your whole self safe while you/they work together with her/him. A body safety plan. ((((safe hugs))))