Can you only tell if have an STD with a pap smear?

A pap smear is a screening test for cervical cancer, not an STD. Some STDs can be transmitted though skin-to-skin contact, so they cannot be detected with a pap smear. Additionally, depending on the type of STD, symptoms may be present that can indicated the need to get tested. Always consult with a medical professional if you suspect that you may have an STD.