What Causes Light Bleeding After Unprotected Intercourse Instead Of Menstruation?

i had taken ipill within 14 hours of unprotected sex (though my husband released it outside , but since it was close to my body i took ipill for protection.). my due date was yesterday. normally i have heavy periods. but from yesterday evening i am having very light bleeding. is it vaginal bleeding? i yesterday morning i did a pregnancy test using pregcolor gold card. there was no single line in T portion but the whole T portion had a light pink shed which went out after 20 mins. am i pregnant/ please help. i am 40 years old.