Please help. I need advice

This is my first pregnancy. I was scheduled for an early ultrasound yesterday because my doctor was a little worried about the viability of the pregnancy. On the day of the ultrasound I was 4 weeks and 5 days. The gestational sac was very small. The tech said it may because I am early. But my doctor will now have me taking test every 2 days to see if my hcg levels are increasing. I am very worried and Google is not helping. Only making me feel worse. Has anyone else ever experienced this.