baby still measuring too big

So I posted at 24 weeks about how I was measuring 27 weeks, I am now 30 weeks and measuring at 39 weeks! I do not have GD and have gained 19 pounds so far. I have a scan coming up when I will be 36 weeks to check all okay but I'm just wondering what happens if they decide baby is too big for my gestation?! Or if there's something I should worry about , about having a big baby?!