Even the most sensitive test won't pick up a trace of pregnancy hormones until you're at least 9 days post ovulation, or 5 days before your period is due. Even then it's less than 50% of pregnant women who will actually get a positive. You tested far, far too early. Wait until your period is due, or, if you must test early, wait until at least 10 days post ovulation. A negative is never definite though until your period is either late or it begins.