Hi Doctor Manjunath,kindly Advice On This,i Had Sex With My

Hi doctor manjunath,kindly advice on this,i had sex with my wife on her 19th 's days counting from her starting Menstrual period last circle on february 2016 ,and she was expecting to start again MP this month after completing a number of 28th days in a month but she found nothing till now which is 30ths and we decide to test UPT and found negative results as well,kindly advice on this matter