Good advice pemsy! I'm 16 DPO and AF is 4 days late. Tested 12 and 14 DPO and got BFN's....even though the first test wasn't a very sensitive test and the second time I tested in the late afternoon after peeing all day, so could have been too diluted...it broke my heart a little bit every time no second line appeared. I'm waiting now for a few more days, using a FRER test and FMU. Leave it as long as possible....every day AF doesnt turn up and u continue to have symptoms is a bonus!