why did I ovulate early?

My cycles are between 30-41 days. My opk was super dark yesterday and today it was COMPLETELY negative. Today I'm cd9. So I should be ovulating anytime between now and the next couple days right? I did BD last night and this morning and plan to do it every 12 hours or so for  he next 4-5 days. But since my cycles are usually long, shouldn't I O later? I'm very confused.