FREAKED OUT!

Ok so according to my LMP I’m suppose to be 6 weeks and 1 day.. when i went to my first ultrasound (vaginal u/s) appointment today the lady only saw a Ges Sac and a Yolk Sac. And she couldn’t determine how far along I am, she said it looks like I’m prob 4weeks.. idk it kinda freaked me out & idk what to expect. Has anyone else had this happen and still had a good healthy pregnancy?