there is definitely a chance. with opks, the normal range is that you can o anytime from the time of the first positive, until 48 hours after your last positive (or, of course, not at all - they arent a guarantee but they are a pretty good indicator.) if you check cm and cp, that can sometimes help corroborate with the opks too. for example, if your opks go negative tomorrow, but your cp is still HSO and you've still got good ewcm, you likely havent o'd yet. if the day after that, cp is low and firm and your cm is scant or really creamy, it's a good sign you o'd the day before. dont know if you do that already, but if you dont, it's a good idea. the other thing that might work well for you is something like the ov-watch.
Every good and perfect gift is from above.