I have had major pain in left shoulder that goes under the arm and into breast. I had a double mastectomy 9 years ago. I have lumps in left bresst?

Without knowing. Your exact history, it is impossible to say, but left shoulder pain can come from heart. Or it could be spread of cancer to bone. It could be something as serious as a fracture or pulmonary embolism, or simple as a sprain, or even shingles. Time to go see a doctor for evaluation for all of these possibilities.