Possible miscarriage?

According to my period, I would be 7 weeks. But I know I'm less than that because we were still living at the hospital with my son 7 weeks ago. I had to have conceived after October 6th... 
Anyway, my first dr appt was last week and I measured at 5 weeks. She sent me to the local lab (not at her office) yesterday for another ultrasound. The tech said I'm measuring 6 weeks 3 days but there's not even a flicker of a heartbeat. She did transvaginal 3D and didn't see anything 💔 She wouldn't give me anymore info. And the doctor said to call the office on Monday. So I have to wait the whole weekend to even make an appt! 
I'm so upset! I have no other symptoms of miscarriage. Is it possible to have a miscarriage with no symptoms?