how did you know you wanted more kids?

I have an 11 month old son and my fiancé and I have been talking about another kid for the past few months trying to decide whether to try or not. I do and don't want another one. I love it just being my Oliver and I but at the same time I think it would be great for him to have a little sibling to play with. My fiancé says he thinks one baby is perfect that we can give him more and he can have a better education and more time with us. I'm just so stressed out about it because I don't want to regret not having another one but I don't know that I want another one either. How does everyone make these decisions lol?