What can cause your breast to be empty and smaller durning your period and then full with slighty tender nipples nine days after i am not on birth control. my cycles are twenty eight days long. it is only day nine of my cycle. my period started on nov 1st

Hormone fluctuations: As you go through your monthly cycle, your hormones (i.e., estrogen and progesterone) rise and fall - going through the process that signals ovulation. As you get closer to the time of ovulation, and then before your period, you may expect more fullness and tenderness of the breasts. I recommend that women having mammograms have them after their periods when the breasts are less lumpy and sore.