Your breasts consist of mammary glands and fatty tissue. Every woman has the same capacity where mammary glands are concerned. These only activate in pregnancy. The fatty tissue you develop is primarily dependent on genetics and secondarily on environmental factors, such as diet, exercise, pregnancy, disease, weight gain or loss. If your breasts have already begun developing, you will certainly reach your maturity by the time you are 18yo. You might look for pictures of your mother and your aunts as teens and young adults, both mom’s sisters and your dad’s sisters, too. If you become pregnant, especially if you carry to term, you can expect an after pregnancy increase of up to two cup sizes, although this is not a guarantee. I once knew a woman who was as flat as a boy. She had had two children and had presumably breast fed both of them, yet remained so flat I couldn’t perceive anything under her garments, not even nipples.
If you are concerned that breast size will affect intercourse, it won’t. While it may affect how males perceive you as a potential partner, a decent, worthwhile male will value you for your personality and your inate qualities and not for the size of your hooters. Believe me, having big breasts is not more advantageous over smaller breasts. Aside for the chronic back pain they tend to cause, the dowager’s humped back, and a profile like a quarterback, large breasts just give rough partners a bigger handle to squeeze. And, for all you males out there, squeezing or twisting a woman’s breasts is only slightly less painful that getting kicked in the nuts.
Btw, ladies, if you need to discourage them, you don’t have to kick them. A flink of your fingertips is sufficient to bring them to their knees.