Not measuring ahead?

I keep seeing posts of everyone saying they're 20 weeks but measuring 26 or something similar. They don't measure me at my OB appts but I did it myself, I'm 20 weeks and I measured myself at ~22. Is anyone else not measuring really ahead with twins. My last growth scan the babies were right on target. I'm a little tired of coworkers and people telling me I don't look like there's two.