What's going on down there?!

Had sex about a week ago, but since then my vagina has been extremely irritated. It stings when I pee and even stings kind of when I'm just sitting here. It's more on one side than the other... kind of feels like an intense stretching feeling, sore but not an achey sore. Kind of stingy/itchy/stretchy... what could be going on? Vaginal tear, UTI, std??? Opinions please (obviously I will be getting looked at by a medical professional as well)