Baby movement

So I went to the doctor today because I haven't been feeling her move as much lately. I'm 31 weeks 5 days. So she did a ultrasound and everything was perfect baby measured 4lbs 7oz and my amniotic fluid was a 12 so that was good. She was moving I guess fingers and hands Moving. The tech said she passed and everything looks good. When I went to see the doctor after that she said I don't know why she's not moving to where you can't feel it since I don't have a anterior placenta but we can monitor you and do a ultrasound every time. I'm just concerned and worried now. This didn't happen with my first except low amniotic fluid. Has or is anyone else going through this. Need some reassurance.