Empty gestational sac.. No yolk sac at 5 weeks 6 days

I went to see gyane today at 5 weeks 6 days. But cannot find yolk sac and only gestational sac can be seen via vaginal scan. I need to go back and see doctor only 2 weeks later. Any mummies experienced the same before and any positive outcome to expect in next 2 weeks? I feel worried if there is anything wrong with my pregnancy.. TIA