Testing 4 weeks post miscarriage

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I had a natural miscarriage on 6/25, I was 9w5d pregnant. My HCG was 26,000 that day, one week later it dropped to 1,500. I haven’t tested again because the doctor said it was dropping as expected. I took a test two days ago, and it came back negative. I tested today (7/23) because I am feeling very nauseous, which was my main symptom while I was pregnant. The first pregnancy was an accident, and we have been very careful, I am still not on BC, but he never goes inside without a condom. I haven’t had my period yet.

Is it possible that this is a new pregnancy? I will test again in a couple days.