What a great question!!!
As for whether I tell my therapist everything...I would have to say No!! but eventually over time he is beginning to find out everything the more I trust him and the more he probes me.
We are also mod/admin on the same forum so he ends up finding out a lot about me that way as well.
I do agree with Embarrassed that there are things like "I google him all the time to find out information about him and I think about him a lot more than I let on" that I don't tell him. I have only recently told him that I care about him and that was as far as I wanted to go with that conversation.
Again...great question