Stressing...

Kiana
My coworker found out she was pregnant before me (like a month ahead of me) and we were both excited and then last week she told she had a miscarriage at 15 weeks :( 
Now I'm worried out of my mind..
I heard my baby's heartbeat at 9 weeks it was 172. I have to wait until July 8th to go back to the doctor..I'll be 13 weeks by then.
I'm so worried and nervous .
Anybody experienced this before?