Like the other ladies have said, that's very early stages for a heartbeat - not unheard of but certainly not something you would suspect. My FS won't do a scan until 6.5 to 7 weeks because he says it causes way too much anxiety in women when they don't see a heartbeat. Even then its an internal scan.

FWIW, I've had ridiculously high hcg levels with the two out of three pregnancies that I had monitored - so much so that my doctors and (this time) the nurses at my FS were all amazed when the scan showed just one. Everyone was expecting twins given the numbers.

Good to hear you're not stressing. Try to sit back and enjoy your pregnancy, although if I'm any indication high hcg levels mean you're in for some pretty full on ms!