8w HCG went down....😔

Last week I went for a u/s and the dr was having a hard time finding the baby. She also stated that I was measuring about a week behind (about 6w instead of 7w) but the gestational sac has still grown normally from the last u/s 2 weeks prior. They sent me to get my HCG levels checked as not seeing the baby had them concerned about a possible miscarriage. On Wednesday my HCG was over 23,000 and on Friday it measured 21,000. The threat of miscarriage is looming so closely now and I’m so worried. This is my first pregnancy and also our first attempt. On top of all of this I am battling an awful cold that I’ve had since I found out I was pregnant so I haven’t had the best time thus far. Anyone out there have something similar happen with a positive outcome? I have read around that HCG can fall as early as 8w if the placenta is growing normally.