Embryo not seen

Tunisia • Mother of 4 little princess & engaged 7.29.16
Hi I'm around 5 or 6 weeks. I've been having some cramps and backache so i went to the er. I was giving an ultrasound and they seen the sack but nothing inside it. They said either it's too early or my pregnant isn't valid and I am in threat of a miscarriage. Was anyone else told this and your baby was okay.