Mrs Ho, you can try monitoring when you roughly O with OPK. With the gals suggestions here, I tried testing from Day 12 with the cheap OPK, until I see two dark lines, then I confirmed it with the Clearblue Digital Ovulation (with Smiley) face. It works, cos' I have difficulty identifying on cheap opks whether the lines are dark or not.
I realised for me this month and last month, i O around Day 15 to 18, even when my cycle is from 30-32days.
I also MC last Dec, so first 2 months, my cycles are haywire. Sometimes, 28 days, sometimes, 26 days. I have gone through 4 cycles since my last MC. Only the recent 2 cycles, I find my cycles normal. I also take chicken essence two times weekly and multivitamins, folic acid according the advice of the ladies here.