Hello,
The various possibilities which present with such pain in the lower left abdomen are diverticulitis, Crohn’s disease, bowel obstruction, ovarian cysts and pelvic inflammatory
disease,irritable bowel syndrome ,
kidney obstruction or pyelonephritis, psoas abscess and volvolus (twisting of the sigmoid part of the large bowel on itself).In your case,it can be due to worsening of IBS.Are you taking any medication for it?