Quoting lauren [+2] TTC#3:" We just started ttc this month. I used OPKs and got positive on CD 12. Checking my cervix it wasn't even ... [snip!] ... Now I'm hoping I didn't O late. Ugh. I really don't even know when I Od just going to assume CD 15. TTC is so confusing. Lol."
OPK's don't tell you the day you O, they tell you when you have an LH surge. Which means O day can happen within 24-72 hours.
Also, are you sure it was a positive? I was sure CD15 I had a positive, but I didn't get my positive til CD17 and started having O cramps within the next day.
I know they say to quit testing once you think you have O'd, but I keep testing to be sure. You shouldn't be having positives for multiple days either.
Assuming you have regular cycles, you should have O'd around the 24th.