Heart rate

Jamie
I had my first ultrasound today. The doctor said I was 6 weeks 1 day even though I know when I ovulated and I'm pretty sure I'm 5 weeks 5 days. I was surprised that the doctor was able to see the heart beat so early but it was only 101 bpm. She wasn't very concerned and said it was so early in the that is to be expected but I just can't help feeling nervous. Any successful stories or similar numbers ? Thanks !