Low hcg, help!!


So long story short, I'm 5 weeks pregnant and was having some bleeding and clots. Yesterday, they drew blood and my hcg came back at 355, which they said was very low. The Dr scheduled me to come back today (then later said they didn't know why they scheduled me so soon, so now i have to have a third draw on fri, I'm kinda mad....) so they took round two of blood. Waiting to hear what my levels are.

If my levels were 355 yesterday, they should double to about 710 tomorrow (at 48 hrs). So is it safe to say that my levels should be 530ish from today (24 hrs)? Is that reliable at all? Also, has anyone else had low hcg?

I'm so worried that we're losing the baby. We've tried for 5+ years an I can't lose my miracle baby :'(