There are a couple of different things that could be happening. One is they misdiagnosed the miscarriage and all is well. It doesn't happen often, but it certainly does happen. The other possibility is that your body did not pass all of the products of conception. Sometimes we miscarry but our bodies do not fully cooperate, and on occasion those levels keeps rising. Certainly not to this extent usually, but I have heard of it happening. Again, not common, but it can happen. Another possibility is that you were pregnant with twins and miscarried one. And lastly, it could be what they call a molar or partially molar pregnancy. Again, very uncommon. Really there is no way to know for certain until that ultrasound. I can only imagine how hard this is for you...the unknown is always the worst. Keep treating your body as though it is pregnant...eat properly, stay away from alcohol, etc. and take care of yourself. I hope this is a misdiagnosed miscarriage. I know someone on these boards that was told during her pregnancy that she had a blighted ovum (a form of miscarriage). Well, that blighted ovum just turned a year old. This is curious..please let us know the outcome.
I don't know what could be going on but best of luck! I will keep you in my prayers! I'm sure this is scary and hard not knowing what is going on! I hope you get great news next week, keep your head up!