uneven milk supply

So my baby is 3 weeks old and for the past couple of days I've noticed that one breast is larger than the other and it feels fuller. She prefers that breast in that she'll nurse for longer on it. I've been pumping the other side when she's feeding about every 2 hours and when I pump the smaller breast I pump longer to stimulate it. Is there any other way to correct this problem? I've been alternating breasts each feed.