I had unprotected sexual intercourse(did not cum inside) with my wife on 31st July...last month she had periods on 17th july...and her cycle is 28 days. Hence, she was near ovulation that time. She took i pill in 2 hrs after intercourse. Yesterday, she took pregnancy test which was negative. Today, she is having very light discharge ( redish brown) with few cramps just like period. Is this withdrawal bleeding due to ipill or implantation bleeding?