Severe constipation from years, tried different laxatives and stool softeners. went for a ct-scan of my abdomen, it was fine. why still constipation?

Considerations...: Further medical evaluation will help rule out metabolic causes of constipation (e.g. Low thyroid or adrenal conditions), distinguish slow versus normal transit constipation, consider a primary rectal dysfunction that may be treatable with biofeedback, check for structural pathology or extrinsic impingement, or intermittent ileus (e.g. Pseudo-obstruction). Any possibility of irritable bowel here?