Interesting that if you met someone "now" that expressed not wanting children you would not get involved. Yet, because you are involved with someone for four years that expresses this not wanting children, you feel that you really have to honor his choice. It's ok to love someone yet finally recognize that this person is not going to be a good "lifetime" match because this person doesn't want the same things you want and this person is adamant in that he "never" wants children. That's a big option to take out of your future so it's understandable that you are really struggling with this challenge. I think you are too young to make that decision, you are really just finding yourself right now too. What if you get pregnant by accident? Does this mean you have to terminate to make him happy?

Personally, I think you are too young yet to make this decision. You have a lot of years that you can bear a child yet and I honestly think you should keep that "privately" open to be a option for yourself. It's "your" life and "your body", not your partner's.