hiya layla, just wanted to say first I didnt realise you had been for your 12week scan yet so I just wanted to say congratulations Im glad all went well and bub sis well, and your in your way to the second tri!
with regards to the measurements I know its a bit scarey when your told its big, When I had the 37 week scan with dylan and his head measurement and abdomen both measured 41 weeks I thought I thought bloody hell! But in the end he was smaller than noah. As your know from your previous scan experiences they arnt ever very acurate, plus it may just be a long baby. Dylan is taller than noah by a couple of centiles but weighed in at nearly 1lb less.
At least its better than measuring small for dates, take it to mean your providing a good healthy home for your bub and its growing and thriving!