Sigmund Freud emphasized the importance of the unconscious mind, and a primary assumption of Freudian theory is that the unconscious mind governs behavior to a greater degree than people suspect.
The only way to tell. The only way to tell if a person has HIV is through the HIV Antibody Test, which detects the presence of antibodies produced by the body in response to the HIV virus. It can take up to three months for antibodies to be developed.
The only reliable way to tell if someone is infected is to get tested. Many people with HIV do not experience symptoms for years after the initial infection or have symptoms that are very similar to symptoms of other illnesses. For more, see this CDC web page: HIV/AIDS Basics.