What the ...?

My hCG yesterday was 5. Still, the hpt I took yesterday was positive and more obvious then the one from the day before, but still ridiculously light- and I had started my period. I'd blame it on that batch of tests, but I used tests from different batches. I've taken enough tests over the last 4 years to know the difference between one line and two lines. I have a follow-up beta tomorrow just to be sure there isn't an ectopic forming.

Since my last hCG quant in April was 3, I'm thinking maybe this was a chemical pregnancy? And it takes longer for urine to filter out the hCG than blood? A non-pregnant women doesn't produce hCG, unless she has certain cancers... awesome bit of information for a hypochondriac like me.