Possible miscarriage

Jill
I'm about to have a mental breakdown. Last week, I had an ultrasound & the heartbeat was 102 at 7 weeks. I just went in today & they couldn't detect a heartbeat. The doctor believes I will have a miscarriage. I've never felt so hopeless. I'm supposed to call for another ultrasound next week. Should I stay hopeful or prepare for the worst?