On November 28th, had sex with husband; On December 10th, had ultrasound check

Patient's question:

On November 28th, I had sex with my husband. On December 10th, I had a B check-up and found out I was pregnant for 40 days. Please tell me if I was in November

Doctor's answer:

Hello, according to the situation you described, this could be due to a detection error or a possibility of pregnancy before. It is recommended that you have another check-up to see. Generally, it is not a big problem. Please pay attention to rest and have regular prenatal examinations.