You can generally tell if you have an STI when something feels “off” down there. STIs can show itself by causing you pain, itching, burning, bleeding or having unusual discharge from both the male and female genitalia.
For example, you might notice yourself getting genital warts after sex, which is caused by the HPV virus.
Either way, these symptoms are an immediate sign that something is wrong. Consult a doctor immediately and to avoid spreading an STI.