AITA for asking my fiancé if he scheduled a workout class with another woman?

This morning, my fiancé went to a workout class and later told me he also went to the sauna afterward. He just mentioned that he went, nothing else. Later in the day, I happened to check the Instagram page of the gym and saw that a woman he used to train was also at that same class and posted a picture with him.

Later on, I calmly asked him, “Hey, I have a question. Did you schedule a class with …. ?”—just a simple question. He immediately got loud, defensive, and blew up on me. saying I’m only asking that out of insecurity. I told him that I would personally feel uncomfortable if the situation were reversed and that I don’t think he would be okay with it either. He just kept getting angrier.

During the argument, he said, “You wonder why I wear condoms with you. You talk about babies, but you think I want to be trapped with this?” I was completely shocked and hurt by this comment. I don’t even know how to process it. It felt like such a cruel thing to say, especially to someone you’re engaged to.

I genuinely don’t think I was accusing him of anything—I was just asking a question. But now I’m wondering if I was out of line for even bringing it up. AITA?