Empty sac!!

Alex
Worried. 
So I had an early scan today sac measurments: 4.7mm x 2.7mm x 4.5mm mean was 4.0mm but there was only a small sac which contained nothing inside the doc said it was really small she couldn't really see inside but she was so unreasurring!! & left me with so man in answered questions when I asked how far I was she said around 4weeks. But some silver fluid was found behind my left ovary! I suffered a blighted ovum 6months ago & really think it's happened again