<human>: i just want to ask, my last period is jan 3 the firs day. and then i had a contact, i made the test using pregnancy test last february 11 2017 and it s negative then i tried again feb. 21 and now it s positive.is it possible it happened like this?? how i calculate the week of my pregnancy. please answer. thank you si much
<bot>: Hello,First, do not panic. The reason for first pregnancy test negative and second pregnancy test positive can be as follows- 1. Delayed ovulation and conception.2. If the first test is not done on mornings first sample of urine, diluted urine can give false negative results. I will suggest you get an ultrasound done to know about the viability and exact gestational age. It will help you to get a clear idea about the number of weeks of pregnancy. Usually, expected date of delivery is at 40 weeks of pregnancy. Hope I have answered your query. Let me know if I can assist you further.