I am in the same boat. I had a D&C 12 weeks ago...yes 12. And I have not had a period. But when they did a serum HCG at the beginning of August, it was 1. So I'm wondering what is happening. I understand that I could definitely be pregnant, but the home pregnancy tests are coming back negative, as did the last time I was pregnant. Any input would be helpful!!!
I would imagine that 7 weeks after your D&C that your original pregnancy's HCG should be out of your system. (based on the half-life of the hormone)
If you were having unprotected sex, you could most definitely get pregnant again prior to a period. I would go to your MD and have a qualitative HCG (or set of them). If they are increasing, you're likely pregnant again.
Good luck!