I am currently using a Medella Pump in Style with 21mm flanges. The problem is that lately, when I finish pumping, I notice that I still have milk when I hand express and I'm afraid I'm not getting all the milk out while pumping. I don't believe that I need a larger size (though not certain); however, they don't make a smaller size. The reason I wonder if I need a smaller size is that sometimes it's hard to get good suction without pushing the flange and holding it tight against my breast. Also, sometimes milk leaks while pumping. Based on the pics on Medella's website, it appears a smaller size might be better (if there were such a thing)- I don't know what to do. I go back to work in 2 months and want to make sure I am able to pump efficiently and effectively. Suggestions? Thank you!