Measuring small at 9 weeks

Hi everyone! I had my first doctor appointment this week. She did a pelvic exam and said I was measuring small for 9 weeks. I have my first ultrasound booked for Monday. I still have the intense nausea. No cramps bleeding or anything like that. But I just can’t stop worrying that something is wrong. I keep checking myself for symptoms. Has anyone experienced anything like this? My doc did not seem worried and explained to me this was a dating scan. I’m positive on the last of my period and know the week i ovulated because I was taking my temperature. Need some help?!?!?!