An STD test is the only way to know for sure if you have an STD. In most cases, STDs are transmitted through unprotected sex, for example sex without a condom (this also applies if the condom has slipped off or torn during sex). If you have not had unprotected sex, the chance that you have an STD is small. Do you have
complaints that fit an STD, such as blisters, painful urination or more discharge than normal? Or have you been warned about an STD, do you have many changing sex partners or is there another one
cause which could make you have an STD? Then contact your doctor or get tested. Take into account the window phase, which means that you can only reliably test for STDs after a certain amount of time after sex. For chlamydia and gonorrhea that is 3 weeks.