4-5 weeks pregnant

Yesterday i went to er because i was having abdominal pain with lower back pain that lasted from the night before and I was scared I was gonna miscarried so i went to er and they did blood work and did ultrasound my hcg level was 3,256 and they said on ultrasound they saw a little ball bt no heart beat and to go back in in two days and they were gonna do blood and ultrasound again....is it since I'm baby a month thats why there no heartbeat or is there really no baby??? I'm so sad thinking I might possibly not even be pregnant has anyone had this and turned out to be just early and was pregnant