I had sex on the 15 of July right after menstrual which ended on the 13th. I took the Postinor 2 on the 16 of July ,and experience light brownish discharge 11 days after for two days. My menstrual cycle was due in the second week of August , and now am in the first week of September,and still no sign of it.I have taken 5 pregnancy test so far ,and all are negative. I took one on the 9th of August , and continued form there my last one was last week Thursday , and it was still negative . I am confused