Can possible ibs cause sudden weight lose?

No: Ibs or irritable bowel syndrome is by definition a relatively benign condition although it can also be quite disabling, too. This is in contrast to inflammatory bowel disease or ibd which carries greater mortality/morbidity & can lead to sudden weight loss. Best to go see your family doc and get checked out. Hyperhyroidism comes to mind but so does colon cancer b/c you asked about ibs. Don't wait.