All the current
guidelines - FDA, testing manufacturers,
CDC, etc. - state 3 month antibody tests are conclusive. As no one in this forum has a medical license, and therefore can't practice medicine, no one in this forum can say that anything but a 3 month antibody test is conclusive.
Now, a negative 6 or 8 week test is a great indicator that someone is HIV negative, but only a doctor can advise to not test further, given the risk, health history, etc.