pregnancy tests off internet........

hi all I brought a bulk lot of these strip pregnancy tests an ovulation tests off eBay I am just wanting a little advice on how to use them correctly as I had my last period on the 10th august an haven't had once since so I am getting a little concerned as to why I keep getting a negative test on these maybe I'm using it wrong I'm not sure hubby an I are ttc baby #1. Any advice would be appreciated thank you