i know EXACTLY how you feel...i'm 20 too and my dream is to be a mother...i wanted it so badly..i actually teared up every time i saw a baby or a pregnant lady...however, after talking ot over with friends and of course my lovely partner, i realised that its not the right time...we DO want kids, but not just yet..we are still uni students...
your need to be a mother wont fade...but think what you will miss when you bring a child into the world...of course nothing i or anyone else can say will change what you want...talk it over with your partner......he has to want is a much as you in order to make a happy family...this is my opinion....just follow your heart and do what feels right... best of luck!