The amount of fat each woman gains or loses in her breasts depends on breast composition, which isn't the same for everyone. If it doesn't go away, have your doctor check it out. When you're breastfeeding, many different things can stimulate prolactin and milk letdown such as a baby crying even if it's not yours , talking about or touching your baby, and sex. Breastfeeding Soon after delivery, you experience a surge in the hormone prolactin that tells the mammary glands in your breasts to produce milk. During the follicular phase, especially five to seven days after your period, estrogen and progesterone levels are low and your breasts are at their minimum volume, says Jennifer Litton, M. You'll also notice your areola and nipples expand. One in particular, Risperdal, is a drug used to treat bipolar disorder. In a study of more than premenopausal women who received mammograms in both the follicular and luteal phase, researchers found that breast density and size was greater in the luteal phase. Exercise In general, you're unlikely to notice any changes in your breasts even with an intense weightlifting regimen. Weight isn't the only thing that impacts breast type. For some, this can be incredibly painful and worsen around your period. But still be sure to have you doctor look at it, Dr. Doctors don't know why this occurs, but if you experience breast pain or "nodularity," as doctors refer to the lumpiness, try cutting out caffeine for several weeks, Dr. Pregnancy The majority of changes that occur in your breasts during pregnancy prepare your body for breastfeeding.