Husband wants another and I do not.

Background... I have 3 children (14,12,10) from a previous marriage and we have an almost 3 yr old together. I will be 37 in Sept.

We got married in Aug and at the wedding he mentioned wanting another. I am a working mom and due to his schedule a lot of responsibilities fall on me. I get really sick during pregnancy and I am a teacher which means I can’t just leave to get sick. I really don’t want another, and he seems set on it. How do we figure this out?!