No cardiac activity 6weeks

Hi ladies, I'm hoping for some positivity. Yesterday I was 6w1d, and I went to the emergency room for cramping last night. They found the yolk sac, and the fetal pole. The gestational sac was measuring at 6 weeks, and baby was measuring at 5w5d. They diagnosed me with a miscarriage because they couldn't find any cardiac activity, they said it's only a matter of time before my body starts to get rid of baby. My HCG levels were at 21,000, I have absolutely no spotting or bleeding, and my cervix is closed. I'm so shaken up and distraught right now, I don't know what to think. Any advice or similar stories would be so beyond appreciated. We have been trying for 2 and a half years with infertility, I can't imagine anything happening to this baby. :(