Hi Debby - If you noticed one of your nipples had suddenly inverted, you'd want to get that checked out, as it can be a sign of cancer. However, with both being affected - and it doesn't sound like it happened overnight - I'd say this is probably just part of the changes your breasts have gone through as a result of nursing. Your hormones are really active during/after pregnancy and nursing, so that may be what's causing these changes. At any rate, if the changes seem to be progressing, and one breast seems particularly different than the other, ask your doctor about them - might as well find out what's going on. Good luck - PJH