Lump in underarm

Amanda • 💙(2/2017); 🎀(10/2018)

So after my son was born and my milk finally came in, I got a lump in my underarm which they said was just the milk "backing up. I'm 20 weeks tomorrow with my second and I have a similar lump in the same spot. Anyone else experience this? Planning to call and ask about it but wondering if I'm alone in that?