why do women breast hurt so bad whn their period is coming?

Question

i never had that problem until after being pregnant.now i cant even lay on them.just brushing up against them is terrible.why is this?
thanks

Answer 1

There are many possible causes for breast pain. For example, hormonal fluctuations related to menstruation or pregnancy are often responsible for breast tenderness. Some degree of swelling and tenderness just before your period is normal.

Common Causes:
Some degree of breast tenderness is normal, caused by hormonal fluctuations from:
Menstruation
Pregnancy -- tends to be more common during the first trimester and pregnancy at a young age
Puberty -- in both girls and boys
Breast feeding
Approach of menopause (once your menstrual periods have stopped completely, breast tenderness often goes away unless you are taking hormone replacement therapy)
Soon after childbirth, your breasts may become engorged with milk. This can be very painful and is usually accompanied by swelling. If you also have an area of redness, call your health care provider.

Answer 2

hormones I believe