Hi, My Question Is About Natural Breast Development... I'm 19

Hi, my question is about natural breast development... I'm 19 and I'm only 30 inch around my bust, which is AA cup, I got my period when I was around 13. My mum and all the women on my mums side and dads side, have C and D cup breasts, plz help what can I do to help increase my breast size? I would be more than happy with a B cup