What causes sagging breasts? i'm 18

Size and Gravity: The best thing you can do is wear a bra, exercise and enjoy your life. Gravity controls all of us here in earth, as well as our bodies. Unless you are interested in breast augmentation, your breasts will "sag" over time, lesser degrees for some, greater degrees for others. It will take some time though, years not months.

Some of the reasons: 1. Large breasts - large breasts sag much more than small breasts from the gravitational effects --- 2. Weight loss - especially multiple weight gains and losses --- 3. Heredity - to some extent it can be familial or hereditary.