I've seen this play out soooo many times. User8563029648123578 is right. He doesn't want to marry you and he doesn't want kids with you. And no, you are not 'so young' or 'too young' and have plenty of time. I first wanted kids at around age 26 (again, I was married), he did the after we buy a house, after we go here, there, after we pay off this. I was 30 by the time we divorced. I was 32 by the time I had my first with now DH. I've had have hung around till I was 30, I might not have had time to have more than 1 child (I started to have miscarriages between DD2 and DS, who was born when I was 37).
He's not at all confusing, he's stringing you along. It's fine to not be ready, it's not to keep someone hanging when you know they're not on the same page. When you love someone, you respect them, you let them go when you realise you're incompatible in a way where there's no compromise. That's what mature adults who love another person do. My ex finally admitted he didn't know when he would be 'ready' but it might be never. That was it.
Sorry, but I'd start looking at leaving. Yes, I wanted to have kids with my ex in particular very much, but no man is worth giving up trying for a family if that's what you really want.
These things always go the same way: either you split up or you give up your chance to have a child for a string along man, who almost invariably has a change of heart when he's in his 40s and decides the relationship has run its course, then goes off and finds a younger model, marries her and becomes Mr Family Man.