Hi guys. You see I'm a teenager and I have only begang to start my sex life, and one of the things that my poor School sex education class left me wondering is when to take a HIV Test.
Do you have to take it after some time after having sex or take it right away?
Thanks

For HIV specifically, most people (if infected) will test positive 3 weeks after exposure. The accuracy of the test increases with time - I think at ~6 months everyone who is infected will test positive. So you could get tested at the 3 week mark, and then a few other times as the months pass.

Also if you have reason to believe that you've been exposed to HIV (like if your partner didn't tell you they were HIV+ until after you slept with them), go to the hospital immediately. There's treatment that can reduce your chances of actually becoming HIV+, but if I'm remembering correctly, it's only effective if you receive the treatment within 1-3 days of exposure.

There are plenty of other STIs to worry about btw, ranging from no-big-deal to inconvenient to deadly if untreated. While you're getting tested for HIV, also consider getting tested for chlamydia, syphilis, herpes, etc. It's common for people to be asymptomatic (showing no symptoms) for a lot of STIs, so it's a good idea to get tested regularly if you're having sex with multiple partners. And if you're not vaccinated for HPV, then see if you can get on that too.

If you're in the US, then try checking out Planned Parenthood. They offer a lot of STI testing & treatment, they're also a good resource for information if Sex Ed isn't cutting it. Not sure if they're able to confidentially offer care to teens, but it's worth investigating. If not, there might be similar organizations that do.