help please ! not sure when i ovulated

okay so i took 8opks. it looks like i ovulated on CD 14 but also CDs 11 12 and 13 also look the same shade as the control line to me..could i ovulate for 4 days??? i want help to know if and what day i ovulated on!! so 1st - CD 8 2nd -CD 9. 3rd -CD 10. 4th -CD 11 5th -CD 12. 6th-CD 13. 7th-CD 14. 8th- CD 15