Welcome to MDC!! 
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If the OPK's are working for you I would say you had a surge on the 21st and will hopefully O within 24-36 hours from that point. What I mean by that is that OPK's are not the most reliable thing for a lot of women. Some women see positives all the time, others never, some see positives well after ovulation, etc. Other things besides an LH surge can also turn an OPK positive. So, OPK's are a helpful tool for some and for others they can be a handy secondary fertility sign, but for some they aren't terribly useful and are just expensive.Â
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It looks like you're dealing with a "half positive" result. Depending on the brand if the outside part of the test band is as dark or darker than the control it is considered positive.  Other brands the dark portion of the test band must also be at least 50% of the band to be positive. Check out this site: http://www.peeonastick.com/opkfaq.html#13. You may need to scour the instructions or call the company to confirm.
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But above all, keep in mind that OPK's do not confirm O- only temping can do that. Do you also temp? Otherwise you could gear up to O with OPK+'s and fertile cervical fluid, but not succeed, and then gear up again in a few days (or even weeks). If you are interested in temping I highly recommend reading Taking Charge of Your Fertility. You can log your temp and CF data on a free site like www.fertilityfriend.com and share your charts with us so we can help you decipher anything confusing. Good luck!