My husband promised me a normal life, a family, and a home, And now she wants to have a threesome

Let me be very clear: I do not support the lifestyle associated with this sub-forum—I am convinced these practices cross every acceptable moral line—but I am approaching this respectfully and simply trying to understand. To be blunt, my relationship is likely ending because my husband told me he wants to be intimate with both me and another woman at the same time. I am not even considering whether to agree to it; for me, it is unacceptable. Although separation was always my absolute last resort—and believe me, I was always understanding with him throughout our relationship—the idea of ​​group sex, of having intimate contact with someone other than my husband, or of him being intimate with another woman, is completely unacceptable to me. Under no circumstances. I suggested that if experiencing this was truly so important to him, he should simply find two other women for it without involving me—and please try to do it without me finding out, though if I did find out, I would pretend nothing had happened. But he wouldn't agree; he said it only made sense if I participated. I don't understand why he wants to humiliate me with something so degrading, nor can I grasp how a man who is truly in love could feel comfortable with someone else touching his wife... Does that mean he never really loved me? That, in the end, I’m just a sex toy—no different from the other women he might use for those kinds of extreme fantasies? I want to clarify that things were good between us; he had shown me many times that he loved me—at least, that’s how I felt—and our intimate life was very good.The more I think about it, the more revulsion and disgust I feel at the mere idea of ​​participating in what he wants; in fact, I would be unable to continue the relationship after doing something like that. Regardless, I don't want the guilty conscience that would come from agreeing to something that goes against my most fundamental principles. Yet, I can't help but wonder where I went wrong—why does it turn out I’m not enough for him? I feel deeply betrayed; he promised me a normal marriage, a stable life, a home, even a family. So what went wrong? What made him change? My mind is full of questions, and the pain is immense. On one hand, the revulsion I feel makes me want to cling even tighter to my values ​​and live an upright life; sometimes I wonder if God is trying to save me from a man who doesn't love me and isn't a good person. But it’s hard for me to believe it was all a lie; everything we’ve shared so far felt very real. I truly felt loved, and I still love him with all my heart... I just want to know the perspective of those of you who have chosen the lifestyle for which he apparently wants to change our home. Do you think there’s any way to get him to abandon this fantasy—or at least agree to satisfy his curiosity with two other women while I’m not present, and then return to a normal life with me? How can I bring the conversation up again? After he first mentioned it, we seemed to go back to normal life, but the issue was left hanging, and I need closure. On the other hand, what could have happened? Where did I fail? Why does he suddenly no longer want a normal relationship and life? Why am I no longer enough for him? Or do you think he never loved me the way I thought he did, and that I never truly mattered to him? I would really appreciate hearing your perspectives