There are very few visual symptoms of chlamydia. The only way to know for sure that you have it, is to undergo testing at a sexual health or GUM (genitourinary) clinic.
The most obvious signs are unusual discharge from the vagina or tip of the penis, and in women bleeding between periods or after sex. If you have any of these symptoms, or you think you may have chlamydia, contact your GP for advice on what to do next.
Your doctor won't be able to diagnose chlamydia on sight, but they can perform an examination with your consent or arrange for further tests at a clinic.