HCG levels after gestational sac. Case?

Hi I had been testing HCG levels every 48 hours since my positive pregnancy test. It was 543.84mi/IU on last Monday . 890 on last Wednesday. 1106 on last Friday. And in Friday's scan Only gestational sac of 3.6mm was found in my endometrium. Doctor asked me to redo a scan on next Friday to see whether I developed a yolk sac and fetal pole with heartbeat.. Today my HCG level is 1471.(after 4 days of last HCG test) my HCG levels are not doubling. But it's raising.. does HCG levels matter after detecting a gestational sac ? I'm so worried bcs today is my 6wks 5 days according my lmp. My doctor said my ovulation and fertilization was too late &that may affect embryos growth.. does HCG levels matter in my case ? I'm really worried.