was measuring 3 weeks behind...

I had a Dr. Appt 2 weeks ago and was only measuring 29 weeks, i was 32 weeks at the time, well i went to my appt yesterday and was measuring two weeks ahead, could it have been the way she was laying? everyone says i look way smaller then i am. my bfs sister is 36 weeks and is measuring that and shes bigger then me, thats why i think it was just how she was laying. i dont usually post many topics so sorry if i dont make sense lol. thanks ladies

u/s can measure off about 2 weeks. So chances of a fluctuation are pretty high!