Stool floats when there's excessive fat in it. You can have a "stool fat test". Reason for fats in stool is fat malabsorption, which may be due to blockage of bile flow (usually bile stone in the bile duct), pancreatic disease with lack of pancreatic enzymes which digest fat, or small intestinal disease...but...first of all, you should have stool fat test.
Would you say the stool is pale, whitish, sticks to the toilet?