I made a joke and may have gone too far. Am I at fault?

My boyfriend, who is 23, and I, 26, have been together for about four months. We have a really lighthearted relationship and joke about everything without a filter. I love to tease, and so do my other friends—it's all in good fun, and we know the right moments for our humor. Last night, I made a joke about having type one diabetes and AIDS, teasing that I was waiting to break the news to him. Of course, I don’t have either condition; it was just a follow-up to another joke we’d made a few days before. He reacted with disbelief, and I thought he was just playing along, as he had done in the past. Usually, when he pretends to believe me, I playfully admit I’m kidding, and we both laugh about it. But this time was different. He genuinely believed me, which caught me off guard. I instantly dropped the act, surprised and apologetic, insisting that I was joking. Unfortunately, it made things awkward between us. He expressed that he felt upset, and I apologized profusely, feeling terrible that my joke had affected him. He admitted to falling for most of my jokes in the past but pretended to outsmart me afterward because he felt embarrassed for believing me. Typically, in my past relationships, joking around has been a bonding experience with those I care about. I told him I wouldn’t joke like that again, and I would have respected any boundaries if I had realized he was being serious. Now, though, I'm concerned it might become an issue, with him feeling like he needs to censor my humor while I feel like I have to tread carefully. I genuinely never wanted to upset him, and I'm committed to being respectful of his feelings moving forward.