I hope all is ok Sarah. I don't think it necessarily means miscarriage. It's not a big difference.

With DD1 I had my HCG tested at 8 weeks. The levels between each test didn't change much and I freaked out because I thought they were supposed to be doubling but my GP said that wasn't the case, that's only very early on and around 8 weeks it levels out alot I also had spotting with that pg and had had a m/c a couple of months before so it scared me too. But all was fine and I had no dramas the rest of the pregnancy.