Like the TWW all over again

[C1nders]

I had my first u/s on Friday and was told that my bub is only measuring at 6 weeks (0.33cm crl) when according to my O date I should be 7 weeks. My OB basically told me to prepare for a miscarriage.
There was a heartbeat, but I wasn't told how fast.
I have another u/s in 2 weeks...
How do I stop myself from going crazy between now and then.
I have no other signs that anything is wrong.
Has anyone else had bub measure a week behind and still had a succesful outcome??
Looking for some hope.
Cindy.