At this point I wouldn't worry, because there is nothing you can do until you have your u/s, and it may turn out that you are worrying over nothing

If she is moving around, and there was nothing else amiss at your apt, those are great signs. The u/s will be able to tell you if there is a problem.
If it's any consolation I had an u/s at 35w that showed Norah measuring 10-12 days behind- but her fluid levels were great, she was moving around, and all her organs looked fine. When she was born she was in about the 5th percentile for weight, but perfectly healthy. Turns out that she was just meant to be small!