Ultrasound help! Miscarriage or twins?

Today I should be 5 weeks 6 days my Hcg level was 16,000 and I had an ultrasound showing my dates to be 5 weeks 1 day with no heartbeat. My dr called to let me know I should prepare for a miscarriage and to repeat ultrasound in 1 week. Has anyone ever had Hcg levels this high and no heartbeat? He said either it’s very early but the numbers don’t make sense or it’s possibly twins. I know it’s a waiting game. I have no bleeding or cramping. Please pray for my baby to stick!! 🙏🏻