After unprotected sex, you know that emergency contraception is possible if you get it in a hurry. Something similar is available for HIV: post-exposure prophylaxis, begun within 72 hours, can reduce the chance of contracting the virus. Photo by Katrina Harrison.
According to getpep.info, you can get post-exposure prophylaxis (PEP) from an emergency room, a sexual health clinic or from a doctor or clinic that specialises in gay men's health or HIV. The course of medication lasts for a month, and NSW Health reported in 2013 that a four-week supply of one drug will cost around $22.40 (though your doctor will be likely to prescribe two drugs).
Other sexually transmitted infections are also a possibility, so it's good to be on the lookout for those too. Read more at the link below for what symptoms to watch for, and what else to discuss with your doctor.
What to Do After You Have Unprotected Sex [Greatist]