Have you consulted with a GI doctor and had any testing done?
first of all, there is a difference between IBS which is irritable bowl syndrom, and chron`s disease.
considering that u r asking about IBS, its called spastic colon too, its a disorder with people who have anxiety , that affects the colon movements usually and make problems in digestion, u could have bloating and pain, usually refered to ur mood status and anxiety or even obsession.
usually, doctors treat this disorder by using SSRI, which is a medication for anxiety, and could relaxes the colon and they give dietary fibers too