Help what do I do?!

Right k know I sound stupid but I'm so bloody broody and can't help being a bit baby crazy at the Mintue I'm nearly 20 and j know I have a lot of things to do before children but the fact is I don't want to do them I've never wanted anything more In life than children I've been telling people this since I was a child and the person in with is the person I can see myself spending the rest of my life with. A baby is something so presious to me and is something that is half me and half the person I love and my SO has said he isn't ready even though he is 5 years older I fell like I'm more mature than my age and am starting to worry that I wouldn't be able to have children later due to a health condition I need your advice and comments on this ladies what do I do!!