6 week scan, no heartbeat. Too early?

Hello! This is the furthest I’ve got in pregnancy after 3 chemical pregnancies all before 5 weeks.

I had my 6 week scan yesterday (from my ovulation calculations I was actually 5+6) I measured perfect but couldn’t see a heartbeat internally or externally.

Dr didn’t seem concerned as she said I’m still v early but should I be worried?! This happened to anyone else?? Any comments would be appreciated Xx