He may have been acting out of caring for you, but what you describe sounds almost as much like gossip as it does anything. Confidentiality in therapy is the single most critical thing. It's of paramount importance. Clients must be able to trust that what they say in that room never, ever leaves the confines of that room and that privacy is respected always.

What tinyrabbit said is true - he actually shouldn't even have confirmed that you are his client, unless you'd given written consent for him to do so.

When I had just started seeing my T, he'd offered to talk to a family member of mine. The family member never called him and I later decided that I didn't want T to talk to her. He told me that if she called, he would politely decline to have a conversation with her. He's also told me that he would not knowingly take on as a client any person with whom I was close, since it would create a conflict of interest for him.

So, I think it may have been a mistake for him to take on your friend in the first place and it was definitely a potentially career-ending mistake for him to discuss you with your friend.