Lower abdominal pain and yellow discharge

Hi, I am a 19 year old girl. For the past two weeks I have been experiencing lower abdominal pain that comes and goes, but it seems to be getting worse. For several years I have also had quite a lot of discharge, that ranges from white to yellow, but recently is more yellow. In these past two weeks I noticed symptoms including : urinating more frequently, urinating smaller amounts, the abdominal pain, and chills. My genital area is sometimes itchy and urethra maybe looks a bit swollen. I went to GP yesterday, thinking it was some type of uti, and he looked at a urine sample which he discarded within a minute telling me I was fine. It doesn't explain my symptoms though. I am going today to gum clinic to get tested for all stds, although I have only had 2 sexual partners, one I was with for a year and a bit and my current partner have been with nearly a year and a half (he was a virgin when we met). I also had a full std screening half way through being with my first partner, and that all came back clear. If today's screening comes back negative, I'm at a loss at what to do next, as I know something is not right with my body. Any ideas?