Confuse

Hai moms..semalam sy pegi check up dkt KK for the first time..bila time last nk scan tu doc kata xnampak..sedih jgk laa..lpastu sy ajak husband pegi klinik swasta utk scan.. ni kli ke dua scan dkt klinik swasta yg sama..masa first tu baby bru 5 weeks.. kli kedua ni supposed to be 9weeks tp bila scan doc kata baby 7weeks.. mcm mna boleh jd mcm tu ye..? tp Alhmdulillah nmpak heartbeat baby..cuma yg sy confused cemne bole jd 7weeks? ada x moms yg ada experienced mcm sy?