Breast tissue in armpit

When I got pregnant with my son 5 years ago, I found out that I had extra breast tissue in my underarm. Before pregnancy, it wasn't noticeable. Throughout pregnancy it keeps growing. When milk comes in, it hardens! It gets engorged just like my breasts. It is so painful and it's like a third boob. I'm experiencing it again since I'm pregnant with my second child. Anybody else have a third boob? 😣 How do you deal with it? Did you remove it?