Hi have i had a missed miscarriage?

hi i went for a scan today, i had believed that i was around ten weeks pregnant, but when i got to the scan they found the yolk sac and fluid etc but no baby or heartbeat and have said that i must be to early i have to go back in two weeks but im going out of my mind with worry, and am very worried that its a missed miscarriage, i need advice has this happened to you