AITA for getting upset and giving up on my relationship?

My partner and I was sitting at home relaxing when his sister called him. She is new to the dating world and needed advice or a listening ear. They were chatting and he was giving her advice as an older brother. Cool, that's a normal thing to do. At the end of the convo, she starts to ask him about his relationship with me. We are fairly new and she doesnt know much about me.. or so I assumed. She asked if we were still together and he stated yes. She asked if we lived together and he stated yes. She went on to ask about a sensitive topic I discussed with him right in front of me. This topic weighs heavy on me even after it has occurred years later. There was trauma and abused with this situation. For him to have casually brought it up to his sister should have been a big and obvious no-no. She only knows a snippet of the situation and when she started asking more questions, he stated "Thats for another convo." Because its clearly heavy and saying anything else about the topic would be insensitive. Just as insensitive to bring it up at all. You brought up the topic and now you cant elaborate on what occurred because its a sensitive topic. Why would he bring it up without my permission? Why would he bring up a topic he couldnt elaborate on as well? This made me stop and think that I am with someone that doesnt care that much about me or wants to protect me. I noticed he will say small things about me to others that I feel he shouldnt. He is the type of person to keep his life pretty private but when it comes to me, I notice he doesnt carry the same mindset. AITA or is my realization that I need to cut him off the right one? Thank you