Today I noticed a lump under my LOs left breast. I've looked around and I found that it could be just from hormones. We are using half formula half breastmilk. Wouldn't she have had the lump previously if it was from hormones, not out of the middle of no where?

* I did notice that the frozen milk we have been using was from a month after LOs birth.. could hormones have been stronger in that milk since It was right after pregnancy/birth and therefore she developed the hormonal lump?