Should I Worry

So today I had my growth scan and something doesn't add up for me, my baby weighs 2.3kg and he still has another month and a half to go. When I ask the Dr as too why the due date changes frequently he said that their aim focus is on the very first scan that was done and that's the most accurate date. I had a scan privately and the scan advanced me 2 weeks as the delivery date. Now I'm confused how come is the baby 2.3kg at 8 months?