Wanting another child but my husband doesn't

I've always known my whole life that I wanted to have for children. When I asked my husband he said he had never really thought about it much. We have three girls now and I really want to try for fourth to see if I can get a boy. But my husband doesn't think that will have any luck. I tried to let it go but it still keeps sticking with me and wondering if I'm just settling for what he wants. I don't know what to do. everytime I try to talk to him about it he gives me the runaround and a bunch of maybes. I don't know if I should make this a make-or-break thing or should I just let it go what do you think?