Ovulation question..

I have been using ovulation tests..and started testing 8/15 and got a neg. Tested again 8/16 and it was positive so we BD that day. Since the 16th I have still been using the ovulation tests (16-23)...is it normal to still be getting positives?? It's been like 8 days of positive ovulation tests! I read online that the normal is 2-3days. And these tests are so dark that the test line is taking dye from the control. And they show up in 2 mins or less. I'm so confused. It's to early for a hpt...someone help please..