Welcome to HCM i have read and understood your query I hope this will be helpful if a guy is sterile,he is unable to get you pregnant secondly if you were having regular periods before,and hv had not sex with any one but him after your last period,he is the one who has got you pregnant. now there can be three possible chances 1. Doctor misdiagnosed him,he must repeat the tests or get a second opinion 2.you had sex with someone else after your last period 3.or most probably you had a false positive pregnancy test if checked by strip method.Get blood HCG levels check and ultrasound abdomen to confirm the pregnancy I will be very glad to know if you find it useful Thankyou Regards Dr Faeza Sherdil