Should I be worried ?

Montano • Mommy of 2 expecting a third by Halloween or early November. I got pregnant with my first at 17 had him in 2016 , had my daughter in 2017 having the next between Halloween and November of 2018
Had my 35 week follow up today. Baby girls heart rate wasn't what it normally is and instead of measuring a week ahead (like I was) , I'm now measuring a week behind . Doctor didn't seemed worried , she said it's because she's getting down into the birth canal but , should I worry??? I go back in 8 days for cervical check .