How long did it take for your HCG to return to 0 after your miscarriage?

I miscarried on June 11, I had finally stopped bleeding on June 26. My boyfriend and I have had sex a few times since then. On July 4&5 I bled again, spotting really, not bleeding. For fun I took a pregnancy test today and it was positive, but I'm not sure if that's the old hcg or new. I know you girls wouldn't have that answer for me. But I am wondering how long it took you all to return to 0.