It sounds like a miscarriage to me, not likely that you are still pregnanct. It can take your body several weeks to get back to a non-pregnant level of HCG. The levels should be rising not falling if you were still pregnant. There would also have been an embryo/fetus on the ultrasound if you were still pregnant. I'm sorry you are going through this. Once your body gets the hormone levels back down you should be able to try again to get pregnant if you so deisre.
It sounds like a miscarriage. In normal pregnancies levels double every 48-72 hours and by 9 weeks they would be in the thousands and only that but they would have been able to see the baby. I am so sorry for your loss.