Thing is with nub theory they can appear to look like a girl nub but then rise within a couple of days, that's why gestation is very important too, my ds3 had a girl looking nub at 12+1on the screen (wasn't captured for the scan picture). However, I'd be very shocked if this one turned out to be a girl as it has very apparent stacking.
Toomuch, for yours I am going to say girl. For 13 weeks gestation, the nub in the first picture still seems long and in line to the spine. Cannot see any stacking; I'm more confident with my guess on OPs scan though.