Hi, Welcome to Healthcare Magic Forum.
It is called Galactorrhea
. It happens when you are Pregnant. If not it happens when there is excess production of Prolactin
Hormone or Hypothyroidism
. Consult a Gynecologist and get a Blood Work up done to rule out these causes. If there is increased Prolactin your Doctor may prescribe you Bromocryptime drug which suppresses prolactin production and effectively treats the discharge.
Good Luck and Take Care.