7 weeks pregnancy but only sac is visible

Hi, if counted from my last first menstrual date, then it should be 7th week of pregnancy while I was having my first ultrasound. However, there’s only a gestational sac with size around 1.12cm seen. No embryo yet 🥲 I know that my menstrual cycle is around 33-35 days in average. Anyone has the same experience? Many thanks and hope everyone is enjoying and having a safe pregnancy and parenting journey!