Worried

Al
I had my first ultrasound today... based on my ovulation- I thought I was 6 weeks 1 day.  My cycles are very irregular, but I was tracking my ovulation.
I had a vaginal ultrasound and my dr. found a sac and fetal pole, but no heart rate yet. She said she couldn't give us a due date yet.  Has anyone had this happen to them at 6 weeks and end up with a healthy pregnancy?
I am going back next Friday for another ultrasound.