If you are post menopausial it can be a source of concern and you should talk to your doctor. If you are still menstruating, there could be a possibility of pregnancy. Leaking and sore nipples are a sign of pregnancy. Take a home pregnancy test, if negative see doctor.
Inflammation of glands and/or ducts and more major health concerns such as cancer may cause these symptoms. Definitely visit a doctor for this and get a mammogram to be safe.
The breast problem may occur due to gaining and losing of weight,emotional stress, prolonged inactivity, excessive amounts of salt,fat and caffeine. The growth in breast tissue are stimulated due to surge of estrogen and proesterone. Sore in the breast may also occur due to ducts in the breasts.