Life changing decision

So my sister had her second baby today. A beautiful little boy. Little logan. While my sister was delivering i was coaching her guiding her supporting her and i realize i didn't want anymore children... It even shocked me. As i was helping my sister i had a realization that i am unsure if i an go threw another delivery. I have 3 children from a previous marriage and my now fiancee wants more. I am just unsure if I'm cut out for it. Anyone else get these feelings while ttc? Btw i posted a pic of little lolo as i have nicknamed him :) i already love him so much.