If you've had sex you might have picked up an infection, and you might not even know anything about it. Sometimes there are few or no symptoms at all, so it's best to take the test anyway. Find your nearest screening venue and pop along - the tests and treatment are free, quick and confidential.

Sometimes there are symptoms, and if you've got any of these things you might be infected and should test straight away. You might get the all clear, but it's important to get it checked out just in case.

• A change in the normal discharge from the vagina
• A discharge from the penis
• Sores or blisters near the vagina, penis or anus
• Rash or irritation around the vagina, penis or anus
• A burning feeling when peeing
• Pain during sex

Some sexually transmitted infections are chlamydia, genital herpes, gonorrhea, hepatitis, HIV, scabies and syphilis. Chlamydia is the most common STI in the UK. It's easy to test for and to treat but there might be few or no symptoms, and if you're sexually active and aged between 16 and 24 there's a free screening programme across the country.