My therapist didn't come out and announce "You have DID." I had/have been in therapy with her for quite a few years. My reasons for beginning therapy were beyond belief depression, anxiety, and being actively suicidal.
Even though I wanted to end my life and my suffering, I have people who need me. I have been living with a chronic pain condition since '99. which has cost me so much I don't even like to think about it.
but anyway, my T was well acquainted with me by the time we started talking about dissociation. so she knew I'd deny it. like I did with PTSD. which she finally got up and held out a list of symptoms of PTSD and asked "which of these symptoms do you NOT have?" which is funny to me now. I knew I had PTSD. I don't know why I denied it.
What my T did was started using new terms, and turned therapy in a new direction.
so I web-searched the terms she was using.
and I felt like the word disintegrated. for the first time.
I read everything I could find on the web. I told my T I was reading up on it. which she wasn't happy with. but she didn't know if I was going to start second guessing her with stuff from the web, or what. but she suggested some books to check out.
I read "stranger in the mirror" and the word disintegrated again, as I could have written a great deal of what I read in that book.
I couldn't fit my head around my actually having DID/MPD. it was impossible. just no way it could be real. so I asked my T if she could recommend a Dr. who could diagnose DID.
She knew a Dr with experience with DID and Trauma, so I made an appointment. I met with her three times, long appointments too. and she said that If I wanted she could write it up as DDNOS, but it was a pretty text book case of DID.
this was a hard thing to deal with as I was the one who wanted a diagnosis to have proof one way or another as to whether I had DID or not. and it wasn't the answer I wanted.
I don't want to make this unreadably long. which I may have done already.
I was running into things I didn't expect from myself. why was I resisting so hard? didn't I have proof enough?

I will stop here. if you want to hear more I will post it. but I don't want to bore you, or write it all out for no reason.

I will say there is a kind of "post diagnosis crash" that seems pretty common. it may feel like the whole world is coming apart. inside it may get very busy. but it will settle down after a while.
it kind of a heavy processing time. and there's lots of new things to accept, and new feelings to deal with.
but it gets better.

jax01