Many moms describe the sensations of let-down (aka “milk ejection reflex”) as a tingling or pins-and-needles feeling. You might feel this sensation deep in your breast as milk ducts force milk towards the nipple. This can hurt a bit at the beginning, as your body gets accustomed to breastfeeding, but should essentially disappear in the coming weeks. Let-down can occur when you're trying to nurse baby…or sometimes occurs if you hear baby fuss or squeal, or simply think of his sweet little face.
While this early discomfort is normal, there are some other potential causes of a painful let-down. For one, your let-down could be more painful if you produce a particularly large volume of milk. (In this case, you'll probably notice baby choking or sputtering during let-down.) If this is happening, it might help to feed baby on only one breast per feeding for a while. Your body and baby will adjust to this in time, and your pain should subside.Other causes of breast pain include: engorgement, a breast infection, a plugged duct, muscle strain or injury, premenstrual pain, fibrocystic breast pain, vasospasms, pumping your breasts incorrectly, or wearing a bra that doesn't fit.