Pregnant after miscarry

I found out I was pregnant August 1st. Everything was great until I found out on the 13th that I was miscarriaging. My blood test went from 3000 to 800 to 12. Now they want me to come in one last time in a couple weeks to make sure my levels down to 0. But once I stopped bleeding a few days ago me and my fiancé started having intercoure again. So my question is has anyone gone for their last blood test and instead of it going to 0 it shot back up and found out that you are actually pregnant again?