I can sort of relate to your situration... I have never had many memories of before I was 12... but resently bits and peices have been appearing (mainly through dreams and flashbacks) and forming complete memories...
I always knew the kind of things that happened though as they went on long after the memory void...


It is amazingly confusing and painful when they appear, even more so for you I am sure as you had no idea that they were even there...
the mind/brain is a strange thing... it can never fully "forget" an event, just sort of files it away. and then at a later date when a similar event occures or once it feels safe these memories will reapear...

give it time. once your mind works out hoe to deal with a few of these memories the rest will be far easier (or so I'm told...). At least you know now... may seem likke a bad thing, but now you can resolve these issues and understand why you have done certain things in your life...

I wish you luck, keep working with your T and let them know how you feel, they should be able to help. No one can "take away the pain" as such, but it will lessen, there will be a way through this.