AITAH for rejecting my boyfriend's ultimatum about an open relationship

My post was deleted in the other sub so I'm reposting here for more input/advice. This is a throwaway account

I'm currently caught in a whirlwind of emotions and relationship drama, and I desperately need advice to untangle this mess. I (24F) have been with my boyfriend (26M) for 4 years. Our relationship has always been great, until he dropped a bombshell on me.

Out of the blue, my boyfriend brought up the idea of opening up our relationship. He explained that he loves me, but he wants the freedom to connect with others (both emotionally and physically) while keeping our relationship intact. At first, I was shocked, and to be honest, I felt a bit betrayed.

When I voiced my hesitation and discomfort about the idea, he gave me an ultimatum: either I agree to an open relationship, or he'll walk away from our relationship entirely. He argued that he needed this, and if I truly loved him, I would support his needs.

This put me in an incredibly tough spot. On one hand, I'm deeply committed to him and don't want to lose our relationship. On the other hand, the idea of him being with someone else tears me apart, and I just can't come to terms with it.

I ended up rejecting his ultimatum, but now he's furious with me, and accusing me of being controlling and unfair. He says I'm stifling his freedom. I'm heartbroken, and I'm questioning whether I've made a terrible mistake.

So, AITAH for rejecting my boyfriend's ultimatum about an open relationship, or should I have been more open to his desires, even if it meant compromising my own feelings? I'm overwhelmed by this situation and need some guidance.