This morning I had my first ultrasound and it was confirmed that I am approx 5 weeks. All was going well until the woman doing the ultra sound said she couldn't find a heart beat and wanted to do an internal ultrasound, after a few minutes she said she still couldn't find a heart beat and she started acting really concerned about it. I've now been asked to come back in 2 weeks to have another ultrasound to see if they can detect a heart beat. When i went in I wasn't concerned about not seeing anything because I didn't think at 5 weeks I would be able to see anything but now I'm quite concerned about the nurses reaction. Is it common not to be able to see a heart beat at 5 weeks or should I be concerned ?

Thanks
Sharon