If you're on the birth control pill, you were NOT having unprotected sex on July 31.
You were silly, if you stopped taking your birth control pills. The birth control pill is one of the most effective forms of birth control there is - it's 99.9% effective at preventing pregnancy. The birth control pill prevents ovulation from ever happening (whether you have a period or whether you don't). Because you never ovulate, you can't get pregnant - not even if he "comes" inside you. n
The 1% failure rate happens when a woman "forgets" to take some of her pills, or stops taking them. Oh, wait! -- you've already done that! Better start taking them again, if you wish to continue having sex and not get pregnant.
"Negative" tests over the last several weeks since July 31 mean you're NOT pregnant.