If he is your age he lacks maturity full stop.
You can't change a man who doesn't want to change. If you have already expressed this to him and he makes no effort to change, sorry to say, but you aren't that significant. Express this to him once more and see if he will at least make an effort. If he doesn't pack your bags and leave to stay unsatisfied.
Break up. If you're trying to change someone.. then it's not good. Break up, and you'll find someone better than him.
there's only so much you can do, you can't make him change if he doesn't want to, maybe you guys should break up!