Help. dont want to be an OLD MOM but husband DOES NOT WANT A BABY?

I'm having rows with my husband at the moment. I would like us to try for another baby by the end of this year, he wants to wait until after Xmas as he is due a promotion. We have lots of money and i have an au pair and i'm a stay at home mum so we not under any pressure. I just feel the sooner the better. My kids are 4yrs, 3yrs and 18 months. I'm almost 25 and I feel I'd like my family complete by 28 as I dont want to be an old mum. Also i'd hate to have to revert to artificial weird stuff like drugs and to feel not like a woman pumping pills in order to do what nature intended. I just would feel very unfeminine if i were to start trying and learn i'm leaving it too late. My doc checked my fertility and he says its like at an optimum. I've got pregnant before within weeks of trying...how can i convince my husband.