How many children do you want?

Has anyone thought about how many children they really want at the end of the day? I'm 23 8 months pregnant with my 3rd baby (second girl). My fiancee and I thought we were done after her, but now he is talking about adding a 4th (not immediately) but keeping the idea open for later because we are so young he is 24 so only a year ahead of me. I only believe I have 4 children in me lol, every pregnancy has gotten harder in its own way for sure I'm almost 33 weeks and I am done right now I can't wait til I am considered full term. Before hand we talked about him getting snipped as it is the easier process, and we have been together for 6 years plan on getting married after I graduate from college. So I am wondering if we should try to keep our options open and if we decide to we will but if not then I guess heavy BC then. I'm just confused just because we had talked about this all before now there is a switch.