If you are not breastfeeding, there may be several reasons. 1, physiological if it is before or after menstruation, or during early pregnancy or ovulation, because of changes in hormone levels, breast ducts will secrete milk, but the amount is generally very small, which is a normal physiological phenomenon. 2, inflammation of the mammary gland, may be due to bacterial infection, or breast extrusion, resulting in breast pain, redness, swelling, local skin warming, and may be accompanied by nipple milk secretion. The actual amount of milk secreted from the nipples may also be caused by the disruption of hormone levels or endocrine disorders. 4. Milk lumps may also be formed by the accumulation of milk during lactation, which may be softened by hot towels and squeezing.