It seems you know all the right things- these scans can be so wrong I don't know why they bother! Know that your body can do this and don't let that fear creep in. I had the same thing told to me about massive baby, etc. I refused the scan because I decided it would be unhelpful to know just how massive, especially given how wrong they can get. DD turned out to be 8lb 10oz, so big, but no giant.

Check out some techniques but don't get panicky about it and make sure your head is back in the right space that you can conquer anything and birth your baby no matter what.