I’m guessing that your first pregnancy was unplanned?
In which case it’s very easy to see why he doesn’t want a baby yet. Very easy to accept and embrace a pregnancy when it’s already on the cards than to consciously decide to have another baby.
I can see why, given you already have one so young, you would want to have another quickly. My parents had me and my sister when they were 20 and 23, but the fact here is that he doesn’t want another baby, and truth be told, even if he said that you could start trying now there are no guarantees that you will fall pregnant straight away. It could still take you a couple of years to conceive and then you could still (in your own words) be popping another one out at 25.
Your language is very petulant and very dismissive e.g. “popping out another one,” it doesn’t actually sound to me as if you want a baby as such, but that you want to fall pregnant again. Why is this?
Having another baby is a life-long commitment, and having two rather than one is much, much harder or so I’m told as I only have one.
Admittedly there’s never a perfect time to have children, but that doesn’t mean that it isn’t something which shouldn’t be thought through.