1 positive pregnancy urine test in the clinic, two negative blood test a week apart

I went in to get an IUD, 4 months postpartum, and the pregnancy test I took before the procedure came back positive. This was a shock, so I did a quantitative HCG test. It came back <0.6, but another was required before we could move forward. A week later another test was ran, the results were the same, <0.6. Two days after the last test, I started having brown discharge, like old blood. My last period was a month ago. I've got an appointment, but it's not for a few weeks now. Should I be worried about pregnancy still, is this a random false positive, or maybe something completely unrelated.