I am a size 6 and wear a medium in almost everything, so you must be on the edge. I know what you mean though, I am smaller than most of my friends and most people would think of a medium as average. I would expect an 8-10 to be a solid medium. Last year I wore an 8-10 and find myself needing larges too. I wouldn't have thought that though, found it out trying to buy clothes. How tall are you and what do you weigh? I am betting we are close in size. We wonder why woman have body image issues?!