Oh, how memory escapes me! I also have DID and I've been told that with a psychiatric diagnosis, that diagnosis stays on your chart even when another professional diagnosises you with something else. They just add diagnosis upon diagnosis; they don't 're-diagnosis' you (you should see my diagnosis sheet in my chart).
So your previous diagnosis still stands (or so I've been told by one of my psychiatric care workers) even though your new T doesn't know about it and the record is long ago and far away.
I would tell my new T about the previous diagnosis if i felt comfortable in doing so... if you did that, y'all could work from there and your new T could assess you and make her own assessment while aware of the prior diagnosis. The prior records are still available to you would be my guess.
I usually don't like to give advice; it makes me feel bossy (i hate being bossy), but I am nowhere near my 'right mind' right now.
I do apologize if i have bothered or triggered you.
And I also apologize for the lengthy post.
And of the subject I spoke of, if you're at all interested in it, I hope you will Google it... because I am not 100% positive that what I said is the actual truth; it is just what happened to me (20 yrs. worth of uninterrupted inpatient and outpatient psychiatric treatment, with diagnosis upon diagnosis with.. uh... bipolar schizoaffective, BPD, and then finally the correct one, DID, with the comorbid symptoms that go along with it... anxiety, cPTSD, and whatever else).
I hope you take it with a grain of salt. .
P.S... If you do actually have DID things get better once it is addressed. And very interesting too! That has been my experience so far.