Is it normal for one breast to be smaller than the other while breastfeeding?

Even during normal circumstances I do notice that my breasts are not the same size. Haha. The breast that produces more milk will tend to be bigger than the other. To solve this problem, offer the smaller boob more often to baby. Always latch on the one with less milk first so as to stimulate more milk production in your lazy boob. Over time the production will balance out and make the breasts relatively equal in size. It worked for me.