having more kids

So I'm 33 weeks pregnant with my first child, my SO has a 2 year old from a previous relationship and he was talking about having more kids. I always said I wanted 4 kids but I don't know I would be pregnant at 22 it seems young but I don't want them to be years apart only may 2 years the oldest. Did any of you start that early and how many kids do you have now? We make pretty good money around $90k a year together but he always get raises.