5w4d Empty Sac?

Went for my first ultrasound. I was unsure of my last period since it was a little weird last month. I was either 10 weeks or 5.5 weeks. I measured at 5 weeks she said. She said it was normal to see just an empty gestational sac this early but I'm nervous. Has anyone else experienced this? I would love to see 5 week ultrasounds and hear how long it took for your baby to be visible on the ultrasound! I go back in 11 days at which point I should be 7 weeks. ****UPDATE: Went back for my second Ultrasound thinking I was 7 weeks 1 day. Turns out I was 6 weeks 1 day and everything was fine! We could see the baby. It was too early to hear the heartbeat but we could see it!