I had an IUI in November. Going by the date of the IUI, my doctor said that I should be 6 weeks 5 days today. I went for my first ultrasound a week ago and we saw only the gestational sac and the yolk sac. Today we saw the heartbeat. My doctor says that I measured 2 days small in both ultrasounds though. He seemed worried. He said that typically once you see the heartbeat, your risk of miscarriage drops to 5%, but since I'm measuring small it could be higher. I have to have another ultrasound in 2 weeks. Should I be worried?