I really, really don't want this to come out the wrong way so please take what I say and know it is not meant in any bad way or as an accusation or anything at all like that, just a question/thought:
you have said before that your mother (whom you love dearly) worked with kids with autism. Is it possible that you adapted into autism because those kids got time and caring from your mother while you were still living in an abusive environment?
Of course, I am not looking to self-diagnose, and I am keeping my mind open to other possibilities. But this is like a record on replay- just as there was with the DID, there are far too many things that "add up" and point to a very high possibility of us having some form/degree of Autism. (Which would certainly more than "explain" Shay).
It's always good to keep an open mind. From what I can remember you're not diagnosed DID so you might want to get that diagnosis first (if it is the right one for you, no one here can tell of course -- more self-diagnosis and all), considering it might play a factor in whether or not a specialist is comfortable setting both diagnoses (if both are correct, I
try to not agree or disagree with the diagnoses that are set/not set because I can't, over the internet or otherwise, see all sides

). I hope you're able to find a specialist who can help you heal and thrive in time