Miscarried and HCG level

Eden

I miscarried July 1st and had my HCG level drawn on the day of and then a week later on July 8th. The first result did show a drop in HCG and the second result showed that it is in the negative range in which they said it was good and to wait till my next period to start the <a href="https://glowing.com/glow-fertility-program">IUI</a> process again. Now I went in to do the cyst ultra sound and HCG draw and found out that I had collapse cyst which was normal after a miscarriage and my HCG level is in the low-high range. I asked the nurse how did it go up if it was negative before? She couldn't answer me and scheduled me for another blood draw on Tuesday. Anyone experience this and might know why?