I recently found a lump between my breast & armpit. I'm thinking it's probably a clogged milk duct but not sure. About 10 years ago I found the lump originally and had it checked out. My doctor said it was just lumpy breast tissue. It hasn't changed over the years until now. I've been breastfeeding for 4.5 months now, and this is my first child. The lump has at least doubled in size and if you look you can see it, but it doesn't hurt at all and there's no redness or discoloration at all.