I had my period last week and everything was normal. On Friday, after a long day, when I took off my bra I immediately noticed a lump right under my nipple that had not been there that morning. It is sore, especially if pressed. It changes size and shape somewhat throughout the day. It does not feel like a round lump, more a swelling of the fibrous tissue. I am overweight and have put on a few pounds over the last month.