No heartbeat at 6 weeks help!

Gaby
Had a scan yesterday showed I was 6-7 weeks pregnant. Could not find a heartbeat so they have asked me to come back a week later and if we can't find a heartbeat they will induce into a miscarriage. I've had no bleeding no cramps. Done a pregnancy test still says positive. 
Is this normal not to hear it so early?
Am I worrying too much?Â