Three weeks lower abdominal pain

Patient: Hi there ,I am 34 year old female, healthy, had 2 c sections, last one was 3 years ago, I have been having this constant pelvic pain now for the 3rd week , started 3 days after I finished my period, it varies in severity but it is there most of the time, feels like burning soemtimes m sometimes my lower abdomen feel bruised as if I just had my c section dew days ago.I had one or two bouts of diahrea, I have more gases now I guess, the pain increase if I walk for more than an hourI had bloods, ultrasound abdomen and pelvis, urine and stoo analysis, fecal occult blood, they all came back negative,I tried duspatiline for ibs, NSAIDS didn’t helpWhat could be the cause, I am really stressed out , and I need help

Doctor: