Empty sac-too early

Molly
So on Friday my fiancé and I went to get our sonogram. Since my last period was May 24 they estimated me at 9 weeks. The sonogram showed an empty sac. Clearly we were devastated but the doctor really thought it was too early and that we may only be about 5 weeks along. 
I took a clear blue easy test on July 4 that said I was 2-3 weeks along meaning it would only be 5-6 weeks at the time of the sonogram. We are headed back in two weeks for another sonogram. Anyone else ever go through this? I'm praying everyday we get to see our baby and not just an empty sac again.