i am 45 yr old female--found a swollen place in my right arm pit about 3 weeks a go went to the doctor she said it was probably an infected lymph node,,,gave me bactrin antibioctic...swelling is gone but the pain went from under my arm to my breast which made my nipple area extremly sore the pain is now also in my upper back and on the outsde of the same arm pit. What could be going on?