Sorry, darlin’. You’re just going to have to accept your small breasts and be happy with them! There are no magic herbs or pills that will enlarge your breasts, including soy. Depending on how old you are, you may still be going through puberty and your breasts can continue grow until your early 20s. Breasts generally increase permanently in size when a woman becomes pregnant, as well.
There are a few herbs such as black cohosh, fennel, and wild yam that increase estrogen, and are therefore believed to increase breast size, but no evidence exists to back up such claims. So don’t waste your time and money on them for those purposes!