Help! Could I be preg?!

Natalie
Last period aug 12. Believe i ovulated on aug 26. Had light bleeding for one day, Tuesday sept 8th. Nothing again until yesterday when I began spotting brown. My periods are very consistent with 4-5 days of bleeding with the first two days being heavy... 
I've taken a couple tests all of which I don't think there's a line? I can't tell! Could I still be pregnant ? Am I testing too early?