About Eight Years Ago I Had A Mammogram And It

About eight years ago i had a mammogram and it was told i needed to have a deep mammogram and a ultra sound on my right breast. I have a crescent shaped mass that goes across the top of my right breast and was told i should have mammograms every 6 months. Well.....it's been six years and now for about a week i am having an extreme pain across my right breast that radiates through to my shoulder blade. I also feels like a lot of pressure inside the breast.
What could be the cause? Cancer runs on both sides of my immediate family. Scared