It is genetically build so no medicine can help increasing growth of breasts.
Take high protein diet like cheese, panier, butter, ghee, puddings, pulses, cereals etc.
Take plenty of green veggies, fresh fruits, dry fruits.
Do regular breast massage
or use breast pump
Take some multivitamin
, iron supplements
Do not feel depressed with small breasts as small breasts are also point of sexual excitement.
Ok and take care.