First ultrasound , not as far along as expected ???

Hi all,

Just curious if this has happened to anyone and what the results were. Yesterday I was supposed to be 8 weeks 3 days along and had my first ultrasound. When I told the tech when my last period was and she did the ultrasound she said “are you sure?” And said I was measuring 5 weeks 5 days. She found a heartbeat (thank god) which was 96 but she said that’s normal for that gestation. She also said she saw two yolk sacs. I have to go back in two weeks to check again but I’m so nervous and also worried as to why my gestation was so off. I’m keeping high hopes as there was in fact a heartbeat. Has anyone gone through this ??? What does it mean? Any and all answers will help and please keep me in your thoughts and prayers . Fingers crossed for a good outcome 🤞