My therapist talked about me behind my back AIO

So this was a while ago but I haven't been able to move past it because I don't know if I'm right to be upset or not. So I'm posting to get others' opinions so that maybe I can find closure.

About two years ago I (22 at the time) lived with a roommate (25M. I'll call him Reese) I had moved in with him because he needed emotional support. I was in a new city where I essentially only knew him. He suggested I go to therapy and I said I would. Reese was always praising his therapist so I decided to see the same one as him. The therapist (maybe in his 50s? I'll call him Dr Kim) knew I was Reese's friend and he had been seeing Reese since he was a teenager.

At first, I wanted Reese to stay with me during my sessions with Dr Kim because I felt timid. I never knew what to say and since we usually talked about problems me and Reese were having it seemed reasonable to me to have him there. But I started to feel like I wasn't being listened to. Reese would say I did something and anytime I would try to explain myself or say it didn't happen the way Reese said it did I felt like Dr Kim didn't believe me or even entertain the idea that I might be telling the truth. He would never, from my recollection, try to get Reese to see things from my POV

A lot of the times during our sessions I wouldn't know what to say and Dr Kim would never try to help me open up or guide the conversation. The longer I was silent the more unbreakable the silence felt. Dr Kim would never break the silence. My friend started not attending my sessions and I felt like I froze up even more after that

Reese accused me of not trying and I always felt that he wasn't being fair to me. I have a hard time opening up and I felt like Dr Kim just letting the silence build made it even harder. I wasn't silent every session, but there were often large patches of silence, just to be clear.

I then found out that Dr Kim had told Reese I was “mentally 15” during one of their sessions and this is where I have a big issue

Dr Kim never discussed this with me. He never told me that. Instead he told Reese while I wasn't even present. After that I didn't feel comfortable with seeing Dr Kim anymore because I felt very disrespected. I would have been fine with him saying I was immature but it felt so specific. It also felt very unprofessional. Why is he disclosing something about another client while said client isn't present? Reese claimed it was because Dr Kim wanted to help him understand me but if that was the case why didn't he ask to see us together so he could say that?

I genuinely don't know if I'm right to be upset about this because of how Reese made me feel. It felt like Dr Kim had talked about me behind my back and violated any trust I thought I could have in him

I'm really just looking for other peoples opinions and thoughts. If I'm wrong to be upset please explain why and if not then I would appreciate an explanation too. I just ask people not to be too harsh. Thank you for your time.