Help !!

Hello ladies , I got an ultrasound today from a calculation from my last period (3/26) which would have made me 8 weeks. I had ultrasound today and I’m more like 5 weeks. They said everything looks normal like it should just couldn’t detect heartbeat. CNM said she’s not overly concerned but wanted to send me for hcg, and normal labs.They then sent me to the lab to get hcg testing and I have to go back in 48 hours to see if it doubled. My understanding is it’s normal not to detect a heartbeat at 5 weeks. She was coaching me for the worst saying it may not be viable, they are slightly nervous about no heartbeat ? Now I’m second guessing and nervous. Do this sound right ??? Anyone had this happen ?