What Cause Milky Discharge From Breast After Tubes Tied?

My tubes were tied 10 years ago- both of my breast are leaking a milky substance- my upper stomach is hard- I took blood tests for pregnancy thyroid and prolactin but everything was negative or normal- I still get my period even though the last two months it was 5 days late but it still came and it was heavy- I haven't had an ultrasound but what is wrong with me?