Hi I Had An Ultrasound At 6 Weeks 4 Days

Hi I had an ultrasound at 6 weeks 4 days pregnant doctor saw a gestational sac and 2 shadows but nothing clear. I have to go for an ultrasound next week. Is it normal to not see even a yolk sac at the moment. Or maybe she did not see anything since her equipment was not good enough. I am getting really worried. She kept saying probably the shadow is the baby but she wasn't sure. Should I be worried for blighted ovum?