Aiyah, frustrating kan when the OPK keeps showing negative! A few of my mum friends pun pernah experience this, sometimes the surge is so quick you miss it, or the timing just tak align dengan testing schedule. Since you've been testing consistently for 7 days and still no dark lines, mungkin worth checking with your gynae or fertility specialist to see if your cycle pattern is different, or if there's something else going on. Jangan stress yourself too much lah, sometimes the pressure of testing every day makes things harder. How long is your usual cycle?