Meant to be 8 weeks- measuring 6 weeks

Is this normal ?

Got an early scan done due to cramping badly, and when the baby was measured it was 6 weeks.

I know the exact date of my last AF. And it corresponds with 8 weeks.

The only positive is I seen the little heart beating . The gynaecologist didn’t seem to bothered by the two week difference and said all my levels were perfect.

I’m now worried as I’m going on holidays in a few days and it’s not a relaxing one but more sightseeing. I should be taking it easy but really won’t be able to.

Can anybody help please. Thank you.