There are a variety of organisms that can cause infections that aren t tested for in a typical STI panel. STI and HIV tests are never 100% accurate. There are a variety of bacterial and fungal vaginal infections that can occur. Normal vaginal pH is about 4. Unfortunately menstrual blood and semen have a higher pH and may alter the vaginal flora that protect from infection. Most pelvic infections occur from multiple bacteria present in the pelvis. A frequently overlooked cause of pelvic infection is Eschirichia coli from the intestine which can easily traverse the vagina and ascend into the pelvis causing symptoms. In other words, not all pelvic infections are from gonorrhea and chlamydia, two of the organism tested for in STI panels. A trial of antibiotics that have a broad spectrum against multiple bacteria, including E coli, may correct these symptoms. Ultrasound evaluation of the pelvis may be helpful. A culture of the vagina to include a bacterial and yeast panel may yield helpful clues as well. See a gynecologist for thorough evaluation of these symptoms. I hope this answers your question, guides you to a thorough evaluation and leads to correction of your problems. I am available for further questions as well.