I didn't chastize him by saying "Why didn't you tell me that before?!", This is what happens or BB will counter with something just as bad. I am happy to hear your situation is different.
I would just respond with something along the lines of "yes, that's exactly the type of thing I need for you to tell me. That's exactly the type of information that is helps me understand better...thanks for telling me." Now that is what I like to hear.
So I guess my view on getting past this is....baby steps, encouragement, and validation of the effort when it happens. Yup, baby steps to build trust. GEL ^5 for getting the job done.