What would happen if you told T all the bad stuff? What might happen?
Sometimes I've found it easier to talk about things in a meta-way. Instead of telling T all the bad thoughts, I'll say "I'm having bad thoughts, but I'm having a hard time saying that to you."
Then, I don't have to get into specifics, I can just talk with T about why I'm hesitant to talk.
For me, it is an issue with authority figures (and maybe other stuff as well...haven't totally solved this one yet.)