Puberty starts when extra amounts of chemicals called hormones are produced in the body. These hormones guide the physical and emotional changes that take place in the body. As you know already, the beginning of breast development is one of the earliest signs of puberty. The main hormones involved are estrogen, progesterone, prolactin, and corticosteroids that drive the development and maintenance of breast tissue, causing fat to be deposited in the breast and the milk ducts to grow. If all of these hormones are released in the proper amounts, it should usually result in the breasts growing to average or normal size. As such, it is important to eat a healthy diet to ensure that your body can develop as it is supposed and help maintaining the hormonal balance. However, every woman is different and her own pattern of growth is pre-determined by her genes which dictate how large her breasts can get.
How can you grow breasts? Unfortunately, as discussed that hormones mostly regulate breast development and growth, there are no reliable means of increasing your breast size other than breast implants or hormone treatments, both of which can carry serious health risks. I strongly advise that you schedule an appointment with a primary doctor
to have your hormone level checked out and to evaluate appropriate treatments.