Heartbeat at 6 weeks help!!

Deanna • I`m 28 years old, married with 2 children!
On Monday I had my first ultrasound and the doctor told me everything looked great!!! BUT she did say that the baby's heartbeat was 80 bpm! She told me not to worry bc it's still early!! I have another ultrasound on Wednesday!! I am so worried about my little peanut!! Has anyone experienced this??