http://www.cdc.gov/hiv/pubs/faq/faq5.htm
This document also available in Spanish
National Center for HIV, STD, and TB Prevention, Centers for Disease Control and Prevention
The only way to know if you are infected is to be tested for HIV infection. Many people who are infected with HIV do not have any symptoms at all for many years. This frequently asked question page includes information on warning signs of HIV infection.