I had an unprotected sex on the 10th day after mensus and used postinor 1after 6hrs,then again had un protected sex on the 17th day,after one week I had a slight bleeding ,which is normal as I ve read,and now this is 28th day and still no mensus,but I have now a big tummy pain and back pain ,pls let me know when exactly I should do a pregnancy test?