I absolutely don’t think he should compromise. He is staying true to himself.
I am not concerned that he isn’t compromising.

I am concerned that you are trying to convince yourself that you don’t want children so you can keep him, especially since he is considering breaking up. You are changing who you are so you can stop him from breaking up with you. That’s concerning

It is nothing to do with who loves who more. But he chooses his true self (not wanting kids) over you and would rather break up than change that. And it’s nothing wrong with that. He shouldn’t be expected to choose you. Him not wanting to have kids is fundamental belief and he holds it to high regard. You on the other hand are willing to alter your beliefs and give up your dreams so he wouldn’t break up with you.

In a long run that’s wrong way to enter commited relationship. Doesn’t end well

It’s also concerning that in 4 years he never proposed marriage. Perhaps his announcement that he doesn’t want children and suggestion you break up or you’ll resent him, could be a hint to you that there will not be life long commitment. If after 4 years life long commitment is still in “discussion” stages and he isn’t on the same page with you, there is a good chance there will be no “happily ever after”.

If you don’t have therapist, I recommend one ASAP.