Birth control pills do not prevent HIV; they only serve to prevent pregnancy. AIDS is caused by human immunodeficiency virus infection. Using condoms can reduce the chances of getting AIDS, but it does not prevent it 100%. The best way to prevent HIV is to be clean, avoid unclean sex and high-risk sex, and not to use drugs or share syringes with drug users. If you suspect that you are infected with HIV, you need to go through a window period of 2-3 months, and some patients may have a window period of up to 6 months. It is recommended to go to a regular hospital or a disease control center to have blood tests to check for HIV antibodies. If the HIV antibody is negative, it is unlikely that you are infected with HIV.