If you are worried you have caught a sexually transmitted infection (STI), it's important that you get tested. It's usually simple to test for them, and most STI's can be treated easily and quickly. The most common infections will only need you to give a urine (wee) sample and you wont need to be examined.
Tests are available at TAZ and GUM Clinic.
However, many people have a sexually transmitted infection without noticing any symptoms at all. If you have ever had unprotected sex, get a test!