Anyone else have this problem? Apparently most people have the opposite problem, since the 21mm shields are extremely hard to find! I even called medela and they werent much help. I ended up finiding them on Amazon. But anyways... if the breast shield is too big, can that cause my pumping output to decrease? DD is almost 10 months old now and I have been using the 24mm shields since birth, but over the past few months my pumping output has significantly decreased and I am having to supplement while at work( I work 3 12 hour shifts per week). Does anyone know if getting the smaller shields would help? I really dont want to have to purchase them and pay shipping and all if they are not going to work. Thanks!