Should I be worried?

Yesterday was my first appointment, before we went we had already done several apps, and pages to find out kinda how far along I am and it was predicted I was around 9weeks and 4days. After my scan, the lady told me the baby was only measuring the size of 6weeks and 5days. They could not find a heartbeat. They will take me back next week to check and make everything is okay, but should I be worried? Or is it still too early to hear a heartbeat?