I had just turned 25 when Charlie was born & people called me a "young Mum", I had been with DH for 6yrs & married just under a year when I got pregnant & people had the nerve to ask "was it an accident"!! I don't think that was young at all.
I would say still in your "teens" is young, you need to enjoy yourself, be young IYKWIM.
Years ago as many have said our parents were having bubs as soon as married, many around 20 & it was normal, now as times have changed we are considered young. But reading all your posts I see another change evolving & I say in a few years you won't be considered so yound anymore.
We do lots for our kids, we live for them. When they leave home you start to "live again (in a different way)" IYKWIM. I saw my parents & my IL's & what they do now & they are still able to enjoy themselves as they are not too aged & sick & that is why we made the choice to have our baby & I aim to have all bubba's before 30.