Please help ease my mind 😩

I went in for a check up yesterday and my doctor measured my stomach. "You're measuring a week behind. You're good." That's all I got out of him until I asked if it was something to worry about. He said unless I'm 2 1/2 weeks behind, then I shouldn't worry. She could've been laying weird he said. Baby was measuring right on time two weeks ago at my last appt. I've been super paranoid ever since I left yesterday. Is anyone else measuring behind? I do trust my doc but I just need peace of mind from someone else. As of midnight, I'm 33 weeks.