Am I miscarrying?

I had slight spotting today which brought me to come into the ER & after both transvaginal & abdominal ultrasounds the doctor says he “thinks” it could be a miscarriage :( has anyone else been through this or knows what it could mean? All labs & results came back good he says, he suggests a follow up ultrasound in a few days but due to the cramping & spotting that’s what he believes... & the fact that they couldn’t detect a heartbeat. I have my first prenatal visit with my OBGYN in 2 days I’m praying for good news