21 weeks and everyone thinks I'm to small

C • C
I've gained almost 15lbs as of 21 weeks.  I know two other people who are pregnant and literally one is a week ahead of me and a week behind me and they are both much bigger than me yet have gained way less than I have. I feel kinda left out of the baby talk because I seem 'less' pregnant than them. 
Any other little bumps out there?