6w scan no baby?!

Moshi • Mummy of Sage Autumn 😍

So I just had a scan at 5w6d since lmp. they saw a sac which was round, and a yolk sac but no fetal pole. They seemed positive that everyrhing was ok, but I'm nervous since so many people seem to see a baby and hb at 6w. Should I be concerned? they said the sac measured at 5w.