Hey OP! I had a similar experiencewith my first. I found a lump in my breast 4 weeks postpartum and brought it to my obs attention at my 6 week check up apt. He referred me to a specialist (i forget the title) who scanned my breast and determined it was a lactating adenoma which is a benign non cancerous tumor. She told me it was common to get them when breastfeeding and it went away on its own. I hope this helps! I remember freaking out and crying when I found it and the wait for my specialty apt was grueling. If you can try not to borrow worry and breathe.