The horns that came with my medela pump were too small so I got the next size up and those seem to big. Which is worse too big or too small? Why don't they make them with smaller increment increases? The next size up was COSIDERABLY bigger. I am wondering if the bigger size might be the reason I am not able to pump as much (got 8-10 ounces in a 10 hour period when I usually get 12-18).