Ahhh don't worry la, irregular periods mmg very common reason tarikh jadi off, a few of my mum friends experienced the same thing and baby turned out perfectly fine! The doc will scan again in 2 weeks and kalau baby's growth on track by then, means everything is developing normally lang, so try not to stress yourself out okay. Insyaallah semua akan okay, first pregnancy memang nerve-wracking but this happens more often than you think!