all babies measure slightly differently, so don't worry, on my 21 1/2 week scan, my babies head was closer to 20 weeks and the femur length ws 24 weeks. Just like people are different shapes and sizes so are our babies, and i was reassured it's perfectly normal. I do have a friend who's baby was measuring big for his age of gestation too, so doesn't mean necessarily yur dates are wrong,although it my be a possibility. If your healthcare provider is concerned they'll keep a coser eye on things with additional scans.
All the best
i wouldn't worry to much i had my baby measured at 33 weeks and his head was measuring 36 weeks 4 days and her stomach was measuring 32 weeks so theres a big difference but remember your baby is still growing so everything will soon slow down o catch up so try and not worry so much