I'm using the medium cups and have been judging my swelling based on where my boob meets the side of the cup- between 1 and 1 1/4". My post swelling measurements are 33 1/2" so I'm not quite the right size to jump up to the larges. But my nipples are getting past 2 1/2" and dangerously close to the tube opening while I'm pumping and I cracked one of the cups the other night without using a whole lot of pressure. So what constitutes filling up a cup? Should I be ordering the larges?