I had an appointment with an ultrasound last week and they were unable to see anything. HCG level was a little over 1000. Repeated HCG levels 2 days later and went up to 3000. I had another ultrasound today and they were able to see the sac, measured at 5w 3d but nothing inside the sac. Is this common so early? They are saying it may be a chemical pregnancy but scheduled another ultrasound for Monday. Has anyone else had an experience of not seeing anything in the sac then normal ultrasound later? Has anyone had a chemical pregnancy? Getting very worried!