It is almost 7 weeks since my D&E and still no period and still getting positive pregnancy tests

I went to the doctor any my HCG is 3000. They're testing again tonight. Based on this number, do you have any idea when I could be down to 0. It seems to be taking forever.
Re: HCG after miscarriage
Have you had an ultrasound to ensure all tissue has been removed, etc?
My Ovulation Chart