Haih, OPK biasanya boleh start dari CD9 or CD10 depending on your cycle length, but most of us test from CD12 onwards to be safe lah, kalau cycle kamu regular 28 days, tengok je mood kamu around mid-cycle, usually around CD14-15 positive garis akan keluar! A few of my mum friends yang TTC dulu cakap better to test twice a day (morning and afternoon) once you see the line getting darker, because the LH surge is quite quick je. Rooting for you, sending baby dust!