Ovulation test

Ok so I'm confused. I am using clear blue advanced ovulation test. I tested on 8/12 and got a flashing smiley face. Had sex on 8/13. Tested again on 8/14 and had a solid smiley face. Any idea of when I could have ovulated? I'm trying to figure out what DPO I am to figure out when and if I should take a pregnancy test. My cycle usually lasts 26-28 days. Last period was 8/4. Due around 8/30. All advice welcome!!