How can you tell if you have a sexually transmitted disease?

You may become aware that you have an STD because of symptoms, or it may be that a sexual partner tells you they have an STD which they might have passed on to you. Some sexually transmitted diseases can be transmitted by an infected person even if they don't have any symptoms.
If you think you might have been exposed to an STD then you should go to see a doctor. Many sexually transmitted diseases can be easily cured, but if left untreated, they may cause unpleasant symptoms and could lead to long-term damage such as infertility. Some STDs can be transmitted from a pregnant woman to her unborn child. It is important that anyone diagnosed with an STD informs everyone they have had sex with within the past year (or everyone following the partner they believe may have infected them).