Did you test at all after the MC? I ask because I remember my dr having me going in for blood work weekly after my D&C to see when my HCG levels were back to 0. I believe it took 6 weeks then two weeks after that af showed. So if there is residual HCG in your body I cant see it creating symptoms if that makes sense.
I tested last Monday and it was -ve so Im confident all left over HCG has now gone