What Does Lower Abdominal Pain, Nausea, Constant Headaches, In PID Patient Indicate

Hi, my a 28yr old female with 1kid. Have been hvn this severe lower abdominal pain, especially on the right. I feel nauseas, have constant headaches, lack energy and irritable. Been diagnosed with pid twice, took the treatment but its not working. My menstrual cycle is irregular. Have a heavy flow. May use 6 to 8 pads a day. Urine test normal and am not pregnant. What could it be?