Measuring small

I am 33w5d. I went in for an ultrasound today, and my baby measured really small, they said she was 3.5lbs and that I had low fluid. My doc was pretty surprised and worried because everything has been fine before today, she thought that maybe my placenta isn't functioning properly and my baby isn't getting enough nutrients. So I was admitted to the hospital. They did some kind of test where I was given pitocin to induce contractions, but not strong enough to cause labor, just to see how my baby would react. Well she passed with flying colors they said, and on the monitor her heartbeat was perfect and she was very active as usual. They are keeping me overnight and doing a repeat ultrasound in the morning and I am meeting with a high-risk doctor. I'm so worried. My doctor said its possible that my baby is healthy and just small, but she is not sure. Anyone else going through something similar, or maybe in the past? How did things turn out?