Dear Dr.,
I am trying to determine if it is possible I am the father of my ex-girlfriend's pregnancy. In two years we rarely used condoms, mostly she took the pill. She had irregular periods, but I know the exact date of last possible fertilisation and results of ultrasound.

Timeline -
October 10 : We are away on holiday, running low on birth control pills so she purchases different brand of similar composition to her regular brand.

October 15 : Her period - 5 days

October 26 : We decide GF will move out of my apartment, we have unprotected sex for the last time. She leaves the country.

November 12 : Her period - 2 days

November 22-25 : GF is away with a male friend. She claims no sexual activity.

December 7 : GF remarks noticeable swelling and tenderness of her breasts.

December 8 : GF takes a home pregnancy test, result : negative.

December 10 : Period does not come.

December 21 : GF takes another home pregnancy test : positive
December 22 : GF takes another HPT : positive
December 23 : GF has transvaginal ultrasound. Results read as follows:

WITHIN THE FUNDUS OF THE GRAVID UTERUS IS A SINGLE GESTATIONAL SAC WITH A DIAMETER OF 1.25CM EQUIVALENT TO 4.3 WEEKS AGE OF GESTATION. NO EMBRYONIC POLE SEEN YET. SECONDARY YOLK SAC IS SEEN.

THE CHORIODECIDUAL REACTION IS THICK, ECHOGENIC AND REGULAR. MINIMAL SUBCHORIONIC HEMORRHAGE SEEN.
MYOMEMETRIUM IS HOMOGENEOUS WITH NO FOCAL LESIONS.

CERVIX IS CLOSED. NO ADNEXAL MASSES SEEN. CUL DE SAC IS INTACT.

IMPRESSION : EARLY INTRAUTERINE PREGNANCY OF ABOUT 4.3 WEEKS AGE OF GESTATION.
VIABILITY UNDERTERMINED.

~ Given the discrepancy in Date of Fertilization and Gestational Age, Is there any possibility that I am actually the father? What are the chances?

Since then she has had 2 more ultrasound (i can forward all 3 images) and an embryo never developed. She says that she was diagnosed with anembryonic pregnancy… and eventually miscarried

Thanks so much