My Boyfriend wants a Threesome and I don’t.

Hello Reddit, First of all, I’m sorry for my English; it’s not my native language. I (f22) have been in a relationship with my partner (m21) for a few months now. At first, everything was going well, but the longer the relationship lasts, the more often we argue about various things.

One thing that’s really on my mind at the moment, and I don’t know how to handle it, is that he has a big fantasy about having a threesome (or generally involving other people in our intimate life). I, on the other hand, am not a fan of this at all, as I believe it would ruin our relationship.

But he is very insistent and says that if we don’t do it in the next few months or years, he would end the relationship, even though he loves me so much and sees a future with me. No matter how often I tell him I don’t want to do it and how much it bothers me, he ends the discussion by saying it will come up again eventually. Since it’s his biggest wish and he can’t explain why he wants it so badly, he just says that’s how he is.

I’m really torn because I’m fighting so hard for this relationship. But this one issue bothers me so much and makes me feel like I’m not enough for him — whether it’s physically or as a person.

Should I try talking with him again? Should I just break up with him? Should I stay and just see how it goes? I really need Advice, maybe I’m just making a big deal out of it.

Thank you guys

(I forgot to mention) He gave me an Example: A person who likes BDSM would never be in a long term relationship with a person who is just Vanilla