Ultrasound too early?

Nelly
anyone else go in too early for an ultrasound?  Went in at 6 weeks based on my period but the sac is measuring 5 weeks 4 days so can't make out much except small smudge inside it.  I think I did ovulate like 3 days later than you would w a 28 day cycle so makes sense - hoping when I go back in a week will see a heartbeat!  Anyone else go in too early?