Most women experience breast changes at some time. Your age, hormone levels, and medicines you take may cause lumps, bumps, and discharges (fluids that are not breast milk).
If you have a breast lump, pain, discharge or skin irritation, see your health care provider. Minor and serious breast problems have similar  symptoms. Although many women fear cancer, most breast problems are not cancer.
Some common breast changes are
  Fibrocystic breast changes - lumpiness, thickening and swelling, often just before a woman's period
  Cysts - fluid-filled lumps
  Fibroadenomas - solid, round, rubbery lumps that move easily when pushed, occurring most in younger women
  Intraductal papillomas - growths similar to warts near the nipple
  Blocked milk ducts
  Milk production when a woman is not breastfeeding
  NIH: National Cancer Institute