Fundal height

Anyone else have any issues with measuring behind? I’ve always been right on the money until my appointment today, I’m 30 weeks measuring 28. I had a private 4d ultrasound at almost 29 weeks and he was 2lbs 9oz. My ob didn’t seem too concerned and said it can be normal especially since he likes to sit low, but scheduled an ultrasound for my next appointment in two weeks. Everything has been smooth sailing so far and I’m worried about this being the first domino, just a little anxious😅 looking for some similar positive experiences I guess lol