No heartbeat 6W1d

On Saturday I went to the ER for extremely light spotting but I also had some cramping so I wanted to make sure everything was okay. They did a vaginal ultrasound and a regular ultrasound and said everything looked normal, but they couldn’t detect a heartbeat. The dr said not to worry because that was normal since the pregnancy is still so early on. Has this ever happened to anyone else? First pregnancy so I’m kind of nervous and just want baby to be okay! First appointment with the OB is in 2 weeks, December 10th.