What Causes Abdominal Cramps And Lower Back Pain With Vaginal Discharge?

Hi, I am having really bad cramping and low back pain. I keep having gushes of watery blood tinged discharge. I am not pregnant. I do have a history of endometriosis. What could this be? Is this urgent? I am scheduled for surgery next week to have my left ovary removed, both tubes and fimbrae removed, a uterine ablation and excision of any endometriosis.