I'm 39 With No Current Health Problems. My Mother Had

I'm 39 with no current health problems. My mother had breast cancer she did not survive her brother also had cancer both aggressive cancers. I have a history of hypo thyroid partial removed back in 2004 taking medication for that no other medication. I have normal periods never had tendernous in my breast. My question is what could be causing my left breast to cause me pain just left of my nipple and just slightly larger. I did have a mammogram last year they found an enlarge milk duct in my left breast. No leaking or skin discoloration it's just very sore no burning or itching. It's been going off and on for about 6 months but it's the worst this time round should I go for another mammogram?what could the possibilities be?