HCG levels. #worried #confused

So I went and got my HCG levels done yesterday and they were 2119 then today I had them done again and they were 4721 so they more than doubled however, when I went in for an early ultrasound they couldn't see a sac. They said they only saw a cystic structure. They said it could be too early as I am only 4 weeks 4 days. I just thought that since my HCG were so high I would at least see the sac possibly even twins. . I just don't understand.

So I got my results for hcg on Wednesday it was 174 and Saturday it is 329??? I still think it's very low but they said it's a defo pregnancy but very early and I need to go for a scan next Tuesday??? And your had low hcg levels what was your 2nd level after 48hrs

Update so apparently I was 6 weeks pregnant went ane last night as I was getting this dark brown cm loads of it, and they done a blood test hcg levels were quiet high, had a scan this morning and there was a sac so they said it was likely a chemical pregnancy but there was a sac seen, so yeah thats the update, they said my last period was most likely implantation bleeding, but im OK at least I know now 🙂 it happens

Scared

My hcg levels r low.. I'm here at the ER waiting to see what they tell me ?

Well ladies, look like I maybe having another miscarriage. I went to the ER for spotting they check my blood confirm my hcg levels are decreasing and they only see a sac no baby. Crazy thing I am not in pain or bleeding not even spotting right now. waiting for something to happen is irritating.