I don't know how to tell you this, other than you have an exactly zero percent chance of having HIV. ZERO!!! A boil on the skin can be cause be a billion things, of course most common is an ingrown hair. If you had been living with HIV for 8 years you would be talking all kinds of issues happening in your body. You would be dealing with a wide array of opportunistic infections. At 8 years living with HIV you would not produce a false negative. No way, no how! After 6 months of exposure you can be 100 percent certain that your test is accurate. You are dealing with health anxiety though. That is much more debilitating than HIV. It takes an average person 8 to 10 years to reach the stage of AIDS. This is a stage of severe compromised immune system where you start to get severe illnesses not seen in the general population. A boil is not one of these. Boils are common in the entire adult population. You would have soaking night sweats, severe weight loss, pneumonia's, HIV related cancers, AIDS dementia, and the list goes on.
HOWEVER!!! Even if you did get to the stage of AIDS and had been living untreated with this infection for 8 years the answer is yes! You are not dead, they can treat a lot of the opportunistic infections and medicines will take the virus in the body and suppress it allowing recovery of some of the immune system. No it will not recover to full capacity, but it will recover and you will live decades longer on treatment. HOWEVER, you are not in this boat at all!!! You do not have HIV, your tests are completely accurate. Oral sex is an incredibly difficult way to contract the virus. You do not have HIV. No way, no how, no chance in a million years. Also remember that HIV in 2013 is not a death sentence. It is not disabling. People with HIV today live completely fulfilling normal lives. They run marathons, they live old and retire from their jobs, they have families, they are politicians, they are grandparents, they are your neighbor, your teacher, your policeman. It is important to recognize that HIV is not a disease to take lightly, but on the same regards it is not a death sentence and for most it is not a disabling disease in 2013. Treat your anxiety and your fear over HIV. You do not have HIV, take peace in that, and know that if you did that there is excellent treatment for it and a normal life and life span is expected for those who do have the illness.