Bleeding, 4 weeks pregnant. Advise?

Im 4 weeks pregnant and currently sitting at the ER waiting on results. About 2 hours ago I started heavily bleeding.The ultrasound look normal for a 4 week pregnancy, but its to early to really see anything to know for sure. The Dr wants me back in 2 days to test my Levels to know if baby is still with me. Im so scared! Has this happened to anyone with a posative outcome?