6.2.15, CD 15.... Did I O already???

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I was trying not to "try" this month, here is CD 13,14 and 15 opks. I feel like I must have ovulated early??? Used to be a 28 day cycle but now more like 30. Any ideas? No sudden temp drops. It has staywd at 97.8 and went up to 98.1 and today back 97.8. In the past I have ovulated on cd15. This month the line seems to be getting lighter.