Low HCG levels??

My HCG was only 56 on Wednesday. On Saturday, it was 161. The first day of my last period was August 28, which would put me at 5w2d. My doctor is concerned that HCG is so low. When I look up HCG levels according to weeks pregnant, I found tables and charts showing that my levels are normal, so

I wasn't worried about it until my doc called this morning and said she was concerned with how low they are.

Please help me out, y'all. Am I losing this pregnancy?

I'll post the HCG chart I was referring to.