The earliest indicators that you may have contracted an STD will look quite different depending on the type of STD, the biological sex of the patient, and will vary quite a bit from individual to individual. The most common early symptoms of an STD including the following: • Changes in discharge and odor from the vagina or penis. • Redness and itching localized to the genital or rectal region. • Painful or burning sensations while urinating, as well as increased frequency of urination. • Small sores and blisters developing on the genitals, rectum, or around the mouth. • Pain experienced during penetrative intercourse. • Flu-like symptoms as your body attempts to fight off the virus or bacteria including a fever, headache, muscle aches, and swelling of the lymph nodes located in the groin.