First ultrasound question

So based on my last cycle I'm suppose to be 6 weeks 3 days went in today for an ultrasound and we could only see the pregnancy with a little faint line in there but no heart beat my dr said I could just be behind on my dates so I go for another  ultrasound on Tuesday June 3 has this happen to anybody and how did it turn out and what should I have been able to see on ultrasound ?