Is it wrong for me to ask if he slept with her?

So a little backstory. Before my bf and I got together, he slept with a mutual friend who we see frequently. It was very weird and uncomfortable for me but of course I was/am never mean to the girl he slept with. The thing that bothered me most was that he didn’t tell me himself that they slept together. I had to ask him and he clearly didn’t want to tell me about it. Anyway we worked through it and I told him to never introduce me to any girl he slept with because I don’t want to be friends with them because it’s too uncomfortable for me.

Fast forward 10 months later I meet this girl who I know is friends with him too. I think she’s nice and we became friends. Later I thought to ask him if he and she ever had a thing. And he got all defensive and said he wasn’t going down this road and wasn’t going to answer. He was all bothered and was asking why I’m asking. I told him how I was planning on having her and some other girls over but I don’t want to start being friends and then find out later that they slept together. So he told me not to invite her, meaning he did sleep with her.

So my question is, is it wrong for me to ask him that? I know a lot of people might think I’m childish for not wanting to be friends with his past ex FWBs, but I tried it and it was too hard for me honestly ☹️ I wish it wasn’t but it is.

Edit:

He didn’t introduce me to either girl. The first one I knew before I knew him, but we all became closer friends. He slept with her a few times then got with me. I didn’t know they slept together until a few months into our relationship.

The second girl was introduced to me by one of his female friends.

To anyone thinking I didn’t want an answer to that question, I do want an answer because I don’t want to have the situation with the first girl to happen a second time. I don’t want to become friends and then find out they slept together and feel weird about it.