Hcg levels question.

Rosalind • Dating my best friend! Our first baby due 8/30/15
My first blood test (2days late for AF) came back positive but my hcg level was only 49.3. Then 4 days my ob calls me to tell me that my levels were so low and I'm probably having a miscarriage. So I went immediately to the ER and got my levels check again.  This time they were 301. They have me in right now to have ANOTHER test to make sure my levels stay rising but I'm just wondering. Are they low? Or are they rising ok?