OPKs & ovulating later

Kristin • Fri, Sep 28

My last period was 9/12-9/15, App said i would ovulate around 9/26 so ofcourse we’ve been doing a lot of BD. Next period is due 10/10 and i thought I’ll do one more OPK this morning and it’s the strongest line yet on day 17??! WTH is going on!! Can i ovulate that late? Or did it already occur??