3 mm fetal pole no heartbeat

I went to my first us and it showed a 13 mm gest sac with a yolk sac. Ten days later my second one showed a gest sac at 22mm and a 3 mm fetal pole with no heartbeat. I have to go back in two weeks for a repeat. Has anyone had this happened before? It was saying it measuring at 5 weeks and 6 days so it would make my dates off by two weeks. However I miscarried two months prior with a d/c. Advice? soooo worried!!!