| Definitely start earlier.......
I had a 33 day cycle after coming off BCP's, this month I ovulated very very early - if I had started using OPK's when the instructions told me to, I would have missed the LH surge altogether!
Also when the line starts getting darker, I would advise you test twice a day - The day I got a positive I tested twice, the first test in the afternoon was faint, and by 11pm that evening was pretty dark.......I Ovulated the next morning, and the surge was gone by the afternoon!
If I hadnt tested twice I would have missed it completely! | 
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