going from 2 to 3 kids..

Can someone tell me if it's really that much of a change? I really want another baby..my youngest is 4 months but I want to get pregnant now so they're all close in age. I don't think that I could adopt or foster and hubby wouldn't want to. He's against having anymore but i think he's just overwhelmed at the idea? How can we come to an agreement? We originally did agree on two so I can't get mad but now that I'm a mom I really want that third baby......