Why do my breasts look small when I wear clothes?

My breasts are 10.5 cm and 8 cm but when I wear clothes (without bra or singlet) they look only 8 cm and 6 cm. I want my breasts to look big because people think I am only 9 or 10 years old because I am short but I am 14. Help please. How do I make my breasts look bigger?