The Dr. Cant explain probably now my

Its started 2 yrs ago! Wen i stop the breastfeeding to my baby. ithink that was starting to show this kind of movable swan inside the breast!(i dont know wat is call that) and accedentaly sudden I felt like a swan. i feel somuch worried that time. but its a good to have menstration i know right after the mens the movable is gone! but in a few days is back again somewere inside of my armfit i was stress bcause until now the movable is not yet gone. I really dont know what it is? i thought before is a swollen lympnodes. So i went to the doctor to check up. and he told me this is not a lympnodes insides in your underarm bcause it is not as inflamed or as painful as other lympnodes. So i was confuse what it is? until now im always checking my arm before. anyway i feel also now my breast is a bit sore. im so confuse! Pls help doctors? give me a piece of helpful advise according to the medical study. Thanks in advance