I have similar issues, with losing myself. Not only with therapists but anyone really. But especially people close to me...
My self image changes a lot depending who I am with, or, who I'm obsessed with.
But yeah, there is a center, a "real me" somewhere...hopefully.
With my T, I've found myself thinking about stuff I assume he's into all the time...and then I've realised that I 've been doing this all my life with people...Even changing my belief system based on this.
What sucks is that I seem unable to talk with my T about perspectives he might not agree with. But I'd need to because it's my therapy..
I understand it's a difficult time for you, so be gentle with yourself