I'm nursing my 5 month old and have always had one breast produce more than the other - nearly twice as much. He didn't latch for the first 6 weeks, so I was constantly pumping and my left always produced twice as much.
Now that I'm nursing exclusively, the left never feels empty - after he nurses or after I pump. And when I pump, I massage like crazy. It doesn't hurt, so I don't think it's mastitis, etc.
Is this normal? Is there any way to fully empty? Or should I be concerned about the mystery lump in there?