How accurate are OPKs?

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Still haven’t had my first PP period, little is 6 months and one week. I’ve been taking internet cheapie OPKs and I had a surge a few days ago. I know it doesn’t ever guarantee ovulation, but are LH surges common while BF? Or can I trust that my period is on its way? I BF about 4x per day and going about 10 hours at night without nursing.