Aww, I understand lah worry ni, firstime mummy things! A few of us had similar scans where HC was on the smaller side tapi doc said still normal range, and honestly babies catch up after born, so try not to stress too much (easier said than done, I know). Best thing is tanya balik your doc exactly what "normal range" means for your baby and if they want extra scans to monitor, because peace of mind is worth it, if they're not concerned, usually it's a good sign! Mana tau baby you just petite, my cousin's daughter was the same and now she's a cheeky little thing lah haha. Keep your follow-up appointments and try to relax a bit, you're doing great!