6 Week Ultrasound - only Gestational sac seen?

Went for an early Ultrasound Monday at what glow calculates as 6 weeks 1 day. The tech was only able to see a gestational sac which she said was "nice and symmetrical" and suggested that it's too early to see the fetal pole/heartbeat. I am scheduled for a follow up u/s next Tuesday. I'm terrified, is this normal for some women?