Are you more fertile at a young age?

ronnie
First let me start off by saying yes I'm 17 i have a 1 year old son, no I'm not to young to have another baby I'm trying to have them while I'm young still. Anyways my question is me and my SO are trying for another baby and were going off by this app to see when I'm fertile and when's the highest percent chance i could get pregnant. Now since I'm 17 is it true that the younger you are the more chance you have to get pregnant especially since your very fertile?