Based on your edited first post:
How regular were your cycles and how long were they?
Also, seeing that you had your first scan at 12 weeks and that measured 6 days ahead of your LMP, I would probably guess (and it really is only a guess) that your due date based on ovulation lies somewhere between the ones from the scan and the one from your LMP. So that means, yes, your baby measures a little bigger, but your LMP isn't 100% accurate either.
So no reason to worry at all, but if you go over your due date, you might have a few struggles on hand to convince them to hold off on inducing you, IYKWIM.
A scan at 12 weeks is at the top end of the time frame where scans are "reliable", so there could be a fair margin of error in there.
You were are "good sized" baby and DH was not tiny either. I bet you both aren't tiny now... So it would be only natural to expect your bub to be a "fair size" - whatever that means.

Saša