Most STIs can be treated, but it's important to get tested if you've been at risk or have any symptoms.
The only 100% sure way to avoid them is not to have sex.
How can I avoid STIs?
The only completely fool-proof way of avoiding sexually transmitted infections is not to have sex.
If you are going to have sex, you need to have safer sex.
How can I know if I have an STI?
The only way to know for sure is to get tested.
You can get tested if you go to see your doctor, or visit your local sexual health clinic.
Both doctors and sexual health clinic staff are very discrete.
However, if you get tested at a sexual health clinic, the results of the test and the fact you've had a test will not appear on your medical records.
Something's wrong down there - what could it be?
The only way to know for sure is to get tested - see your doctor or visit your nearest sexual health clinic.
Who can I speak to if I'm worried?
The best plan is to get along to see your doctor or visit your nearest sexual health clinic.
If you just want to talk a bit first, you can call Childline free at any time on 0800 1111.
For more information about STI's watch this interview with a sexual health advisor.