6 weeks and no baby

I just left my first doctors appointment and they saw a sac but no baby. I am also measuring early at 6 weeks instead of 5 weeks and 3 days. With my daughter I was able to see a heart beat at 6 weeks and 3 days. I'm really scared. The app is also stated that at 6 weeks you are able to see a heart beat. They want me back in 2 weeks for another sonogram. Please give me hope ladies because I can't face another miscarriage. I'm in my car crying