What Causes Yellow Vaginal Discharge And Swollen Inner Labia?

Hi i am a 28 year old female, i have recently had rough sex with my boyfriend, the day after has left me with a swollen labia inner, excoriations bilatrally on either side of the labia inner, i am getting a yellow discharge and it is very painful to sit, walk and urinate! It is now 4 days since we had sex and it is no better. We have both been tested for sti s at the beginning of the relationship and were both clear. There was another instance 2 years previous where the same thing happend to me, i went to my local gum clinic expecting the worst and all tests were clear and it cleared up on its own. I was wondering if you had any idea what this could be and how long it is likley to last? Thanks