No AF and neg hpt

This is my 4th cycle TTC and my period is 9 days late but I took 2 hpt both BFN. First hpt on cd28 (3 days after missed period) this was last Wednesday and BFN, so I tested again in Saturday cd31 and BFN. Now I'm on cd35 still no AF...should I test again? I'm not sure exactly when I ovulated this month bc I was using opk but just got 9 days of flashing smiley "high fertility" never a peak. But we BD'd every other day during fertile days. Wondering if I just missed period this month and if I can/should start opk again, will I ovulate this month? Want to either know if I'm pregnant or if we can start trying again???