I am always constipated, why is this? my stool are always pebbles.

Scybalous stool: Hard pellet-like (scybalous) stool, associated with passage of mucus, suggests several possibilities: constipation-variant irritable bowel syndrome (c-ibs), rectal dyssynergia due to altered rectal tone/sensation, partial obstruction likely due to adhesions. Work-up may include: colonoscopy to evaluate the bowel, sitz marker testing to distinguish normal- versus slow-transit constipation, ct scan.