No heartbeat at 8 weeks and 3 days

I recently went in for an ultrasound and they told me that I was 8 weeks and 3 days...you can see the baby, the sac, etc. It was a very exciting and emotional feeling, this is my first child. But the only thing that lady couldn't find was a heartbeat. Apparently, there should be a strong heartbeat by now but I didn't get that.

Now, what does this mean? Has anyone gone thru this?