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?
Investigations like ultrasound abdomen, CT abdomen and colonoscopy are required to confirm a diagnosis.My advise is to consult a gastroenterologist and discuss these possibilities with him.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.