How fast after sex can you test for hiv?

A negative result from a test done too early does not exclude HIV. Get a 4th gen combo test 6 weeks after exposure. HIV is only one of the STDs. Even a condom may not protect against HPV, Herpes, LGV, syphilis, pubic lice etc. It would be prudent to see your doctor for an evaluation. Visit this site for information: https://www.cdc.gov/std/default.htm Wish you good health!