Hey hon, welcome to this side of the forum and kudos for coming real with yourself about it and reaching out for understanding and help. Now the healing can begin.
Not many people will take DID seriously, especially if you all of a sudden proclaim it like your psychotic or something. Nobody here, family or even professionals took me seriously, even on this forum I think they thought/think I'm nuts! :P I asked my new pdoc what he thought about DID, he didn't even know my name and said that I don't have DID! He's fired. This is a real lonely condition because it's like unbelievable that it would happen to someone they know, just to others on a planet far away.
I'm 47 also and there's copies of my story on here everywhere, we pretty much came out of denial a year ago, but have known since we were 8. We switch and take turns running this body for it belongs to all of us. Everyones system is different, but I understand what you describe.
I call myself a multiple because I'm pretty much undiagnosed, but it's obvious and I'm co-con. I'm okay with floating around DID and OSDD...I can probably be called either because I have like almost no memory of things, just bits and pieces. There is nothing in disability that matters about having DID or whatever, so having the official DX doesn't matter. Testing is for those that aren't aware and having living problems because of it, and to weed out the wanna be's which I don't get.
You can forget convincing your T about your condition I think. I looked up a T that specializes in trauma and dissociative disorders, walked in there and said skip all the testing crap because I know, told her my story, and said lets get on with the healing....she was into it. Unfortunately, she doesn't want to start integration process till I can afford it.
You sound like a multiple because you are so confident in what you say with the right history.
What I did though is I started keeping a notebook doing journaling. I also wrote out a timeline of experiences, my quirks, dissociation times and triggers....I call it my DID notebook. I mapped my system with descriptors of each ( we got hundreds of others- we hate the word alters). It's on my iPad, so it goes everywhere I go.
Got to go but hope to hear more and let's discuss.