HCG levels

How long did it take you HCG levels to go down? I found out July 8th my baby’s heart stopped at 8 weeks (I was supposed to be 10 weeks). On the 13th I started to miscarry and bled for a week. The week after that I took a pregnancy test to see if my levels went down and it came out negative. But Friday I tested after having cramping and spotting and it was a faint positive. I’m still testing positive but very faint. Is it possible this can be leftover HCG or can this be a new pregnancy?