Possible miscarriage?

Mac

Hi ladies! I need some help because I am so confused about whats going on. I am pregnant and started bleeding last Wednesday. Based on my period I would have been around 8 weeks, based on my ovulation, I would have been like 6-7 weeks. Anyways I went into the doctor the next day and he did and ultrasound, we could see the yolk sac but not a baby. He said I must be earlier than I thought. To find out if I was having a miscarriage we did a blood test Thursday and Saturday to see if my HCG levels were doubling. I got my results back today and am even more confused. Based on my HCG he said I should be 8-12 weeks, and my HCG did go up but didn’t double like he was hoping to see. But if my HCG levels are that high, why couldn’t we see the baby last week? I’m going in for another ultrasound tomorrow but if anyone else has experienced this help!