Pregnancy after miscarriage

Amber
Soo, February 4th drs told me I was having a miscarriage at 6 weeks. After all bleeding stopped, I waited a week or so and took a pregnancy test that came back negative. I never got a period after, so yesterday I took another test out of curiosity and it came back positive. So my question is, how can I tell when i concieved? I've made a dr appt, they want to test my levels.