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Its good that you have had testing and cultures have been negative, because if those infections go untreated, they can cause problems. The pelvic ultrasound and bloodwork sound like a good idea. You may have a resistant form of a urinary tract infection and need an extended course of antibiotics. If the thrush is still present, it can also contribute to symptoms of discomfort, so completing the medication may help symptoms. Taking Ibuprofen can help with pain and inflammation if that is the cause.