The various causes of breast soreness are premenstrual syndrome, hormone therapy, pregnancy and breast feeding, fibrocystic
disease, use of oral contraceptives and rarely a breast
malignancy. Please consult a gynecologist and discuss these possibilities.
In absence of pregnancy, it can be due to hormonal imbalance and should improve with time. Apply warm compresses and take some anti inflammatory pain killers. If it persists then get it evaluated from a gynecologist.