Measuring too small

Izzy
My doctor had to schedule an ultrasound because I am measuring too small. He said it could be the babies position and not to worry but I have to wait until next week to find out if everything is okay. My last visit was at 28wks and I measured 28 cm but was also very constipated. At 30wks I am measuring at 26cm. Has this ever happened to anyone else? I'm trying to stay positive but I'm also very nervous. I made it this far so I'm hopeful that there won't be any serious problems. My baby is very active and the heart rate was at 150 bpm