My goodness, elmum. What a rollercoaster for you. I'll share my story as it may be helpful to you.
I MC (d&c at 8.5 weeks) on August 2. We found out baby had no heartbeat on July 20, tried the medication option which did not entirely work, so my levels were dropping for a week and a half before the d&c was needed. A week after d&c I still tested positive on HPT and took OPKs and those were also positive, likely because of HCG. I was taking IC's at this point not wanting to waste money on expensive tests. I got a negative IC HPT on August 18 and I was happy!! A week or so later I got a positive OPK and that combined with a temp rise, looks like I ovulated on August 26. Started having weird pregnancy symptoms, my breast pain returned (it had gone away) and increased CM, same I had with my pregnancy. Took an IC and thought I saw a faint positive (I was driving myself crazy) so I took a FRER and got a vvvvvfl. The line got slightly darker but was still vvfl. It then would get lighter...it was so confusing and I wasted probably $70 on FRER, but I never got a hint of another line on an IC. I am not sure if it was residual from the MC, or a chemical, but AF arrived 5 weeks and 1 day after the d&c (truly the worst period I have ever had, so painful). It can take some women a lot of time for HCG to go to zero, and it can still fluctuate...the normal I think is 2-8 weeks (a large disparity!)
I hope for you this is a new pregnancy...fx!! xo