5-6 weeks pregnant - no heartbeat at scan

I found out last week I am pregnant and told the doctor I’ve had cramps and also wasn’t sure when I’m due, I got an early scan appointment two days ago. The sonographer who did my scan did tell me before it could be too early to hear a heartbeat. She could only see the sack and yolk sack and said that’s normal for 5-6 weeks. There was no detectable heartbeat yet but they kept reassuring me not to worry and it’s so common this early to not be able to hear it but I keep worrying! They said I don’t need another scan till 12 weeks but I can’t help but worry :( anyone else had this? I also haven’t had any morning sickness yet, am I just ridiculously overthinking? Help someone