A mother's milk doesn't come in until 3 to 4 days after the baby is born. In the meantime, the baby sucks very small amounts of colostrum from the breast. Some hospitals give baby formula. I hear in the olden days, Moms gave their babies water while waiting for their milk to come in. Being stressed out or tense can delay the milk from coming in. When the milk does come in, it hurts. It feels like someone tried to stuff too many oranges under your skin. Letdowns— a reflex that releases milk from the breast, usually activated by the baby sucking—can hurt too. It feels like someone pressing on a bruise from the inside mixed with a tingling-like, appendage-just-fell-asleep sensation. When nursing and experiencing a letdown, both breasts release milk, and if you're not wearing nursing pads, you may leak onto your clothes. Letdowns occur even when not nursing or even thinking about your baby. They happen when you aren't ready and aren't wearing nursing pads.