Possible to see an empty gestational sac during ultrasound at 6 weeks?

Based on my last menstrual period, I should be at my 6 weeks now. However, during my scan yesterday at 5 + 6 weeks its shows an empty gestational sac with no yolk or fetal pole. Doctor says that the gestational sac indicates that 99% baby is in the womb and not an ectopic pregnancy. But I can’t help but feel very very anxious before my next scan on 25th! This is my first baby.