12 week appointment

Doctor said I was 12 weeks and used the Doppler today and we found no heartbeat. He said come back in two weeks and we should be able to find one! Now I'm worrying and I can't stop thinking about it. I've had no bleeding or cramping but I hear that sometimes doesn't happen. I'm seriously freaking out and I don't know what to do! This didn't happen with my other two babies. I heard them as early as 9 weeks via Doppler :(