I've been with my boyfriend off and on for 10 years now. To make a long story short, while we were not together he had 3 children (4 y/o and 3 y/o twins) with his now ex-girlfriend. A couple months ago we had an unplanned pregnancy and I had to choose staying with him or keeping the baby, I chose him. I've tried talking to him in the past about having one of our own and he says 'no, I'm not having anymore.' I want to try and bring up the conversation again because I would love to have at least one child with him before we turn 30, which is in 3 years. My only fear is how can I let him know that it hurts me to hear that he never wants to have children or even consider changing his mind in the next couple years?
For many people, perhaps most people, having children is a completion of their lives and they would not truly fell fulfilled without them. However, not everyone feels that way and that isn't necessarily a wrong or selfish choice. Also, some people feel that after so many, they are complete and don't want any more children. That isn't wrong either.
If having children is that important to you, you are going to have to make a choice. At least your boyfriend is being honest with you and telling you what he wants, not stringing you along saying "maybe in a year" or "maybe when we've saved some money." He's saying flat "no." Even if it hurts you, he can't help how he feels any more than you can.
Perhaps it's time to face the fact that you don't want the same things out of life, out of your future together. You don't want someone you're going to have to talk into being a father, do you? You want someone who can't wait to have a family with you. Those men are out there. You mentioned that you've been "off and on" which makes me also wonder if there aren't other issues in the relationship, as well. Just because you've invested this much time in him, doesn't mean you have to invest more. You're only 27, you have time to find the right person you will be compatible with going forward.
Another danger is that he ends up caving and you have a child, but he still doesn't really want it. What kind of father will he be if that is the case? You want him to jump in with both feet. You deserve that and your children deserve that.
Best of luck to you. You have a lot to think about.