my daughter is 13 years , she had abdominal pain around the umbilicus for 15 days now , she has low grade fever 37.4-37.6 , since about 10 days she started to complain back pain that extend from thoracic to lumbar region , she has hihg WBC count with neutrophilia , but normal other CBC parameters , urine & stool are free , abdominal ultrasound shows nothing , since about a week she started to complain also ankle pain but no signs of inflamations , she already receaved ceftriaxone 1gm injection for 5 days & paractamol 500 mg twice daily , but she improve temporarly then complain again , now i am confiused , what is the cause & why she is not improving ?