I bought some cheap OPKs called 'one step' off the internet. I starting testing from about the 8th day in my cycle (my cycle is regular and 28 days), doing one in the morning and one on an evening. Every test has two lines but the control line is darker and the test line doesn't seem to be getting any darker. My app now says today should be my ovulation day but still no sign of a darker line. However i have noticed a change in mucus and I have had slight cramping but still the test is still showing negative. I came off to implant end of June but periods have been regular since.