It is very common for women to see a drop in supply when their period returns - typically it will be in the days leading up to, and it will gradually get better. The good news is, this is typically temporary. It can just be frustrating! The best thing you can do is stay hydrated, nurse baby as much as they want (even if it seems like they are constantly at the breast), and be patient. There is some evidence that suggests taking calcium and magnesium together can help combat supply issues during your period. Please see this Kelly Mom article for dosage information - but always consult with your doctor first!