Low heart beat at 6week

Hey guys, well for starters my anxiety is on 1000 right now and I’m so filled with worry. I went in for a ultrasound on 05/09 due to the doctor not being able to find the heartbeat at my last visit on 05/08. My doctor was concerned because I should have been around 7w +5d. After the ultrasound was done, I was then told that my due date was off and that I was only 6w +1d. However the heartbeat was only at 82. Have anyone experienced such a low heart beat around this time frame and had a healthy baby ? I’m really concerned and just looking for hope.