Can I ask why you turned the aging off? If you don't have a reason for it, why continue with it off?
I play with aging off, and I can say that as far as I've seen, not even babies age up at all unless you use a birthday cake. I count the days for my sims so I know when to age them up. My reason for doing that is because I want to play the whole neighbourhood without stuff happening to the other families while I play one family. But most people keep aging on.
Turning aging off doesn't stop your sim from getting pregnant and having the baby in the normal 3 days. So you can still get your sim to get married and have kids, which would be a way of getting more sims, but you'd have to age up the child with birthday cakes. If you're just worried about losing your sim if you have aging on, there are other ways of keeping him young, like life fruit, the tattoo glitch, and ambrosia.