Scared baby might be dead.

I had my last scan at 11 weeks. Saw the baby and heartbeat. Had bad morning sickness and other symptoms also. But starting to worry now baby might not be alive. Symptoms disappeared shortly after the 11 week scan and no bump at 11 weeks either. Im now I'm 18 weeks 4 days and still no bump, not even a little one. No symptoms either. My next scan is 21 weeks. Should I be worried and all a doctor/midwife? No bleeding or cramps though. Advice please? Thanks.