If you think you may have chlamydia, there are a few things to check for. The first is to see if you have any symptoms. These can include a sore throat, fever, and swollen glands in the neck or underarms. If you do have symptoms, it's important to see a doctor as soon as possible so that they can diagnose and treat the infection. 
The second way to know if you have chlamydia is to take a test. There are different types of tests available and they all work in different ways. Some tests require you to take a sample of your urine and send it away for testing. Other tests use a swab taken from inside your mouth. 
If either of these are difficult or impossible for you to do, there is another type of test that can be done on blood samples.