A woman's body, including the breasts, can undergo modifications throughout her life. When women put on their breasts they tend to increase in size because they are shaped by fat and the opposite occurs when the woman slims. Before menstruation they tend to be larger because of the hormones. When the woman becomes pregnant for the first time, the mammary glands complete their development and the breasts tend to become larger. Some women have a large growth of the breasts during gestation, but the breasts tend to regress, in part, after she stops breastfeeding.
Talking about growth that occurs in the juvenile phase, usually it is around the age of 18, but it changes very little after 16 or 17 years. So in your case you're 17 years old: the body you have is this, it will not change much.
