AITAH for not covering my boobs in a sauna?

23f, my boyfriend and i are in Germany rn. I love saunas, so our first night there I was super excited to check out the spa. The steam room had a sign saying that it was a "textile free space". While that wasn't a deal breaker to me, I figured it wouldn't be a good idea to go in without asking my boyfriend what he thought first, so I left. So yesterday I asked him what he'd think, and if it would be ok if i went. He said it sounded exciting and said he'd come too. We go in, naked, obvi, and put towels down. We're the only ones in there for about 10 minutes, and a couple of guys come in. I don't pay them any attention, and if they were checking me out, I didn't notice.

After about another 15 minutes my boyfriend nudges me and makes clear that he wants to go, so we do. As soon as we get out he's furious at me. He tells me that he can't believe i let other guys see my boobs, and he was expecting me to cover them with my hands or something. I told him I was really sorry that I hurt me, but I thought it was implied that if we were in a public steamroom, there was at least a possibility other guys would see my boobs. I told him I wouldn't be upset if another girl had come in and he'd seen her boobs, it wasn't supposed to be a dirty thing.

He told me that it wasn't at all implied that other guys would see my boobs, and that it's extremely disturbing that i was okay with that.

AITAH here? How should I approach this going forward?