Breast asymmetry after breastfeeding is not unusual, and if there has not been significant sagging of the nipple and breast tissue below the breast fold, it can be corrected with breast augmentation. The breasts often appear to be not just smaller but "deflated". If the two breasts end up being different in size, the key question is which side has the most breast tissue, not just the most excess skin, and this question can only be determined with a physical exam. In the meantime, one way to get some idea of which side has the most breast tissue is to see which side looks and feels bigger in a good, supportive bra. Even if you need a breast lift, this type of situation can often be treated with a periareolar breast lift, in which the only scar is around the boarder of the areola skin of the nipple.