STIs are common and can present with or without symptoms. So how do you know if you have one? In this video, Susan Khalil discusses what common STI's are and what you can do to prevent and treat them. Some STI's can lead to other infections such as a pelvic infection, as well as causing you to become infertile. Around 1 in 5 people have reported having STI, so if you are in doubt about whether you have one or not, ask an expert.