Confused!!

Brittany

So I'm 3 weeks and 4 days post d&c and I'm getting positive test that seem to be getting darker. But I had blood work drawn and hcg levels were 18 on 8/1 and then today 8/4 and my hcg levels are a 9. But how is it possible that my hcg levels are that low but getting a positive home pregnancy test that's supposed to measure 25 or higher of hcg???? I'm so lost! Could I be pregnant or am I crazy