Mix together the cream of chicken soup and milk in a small bowl. Pour enough of the soup into a slow cooker to cover the bottom. Layer chicken breasts over the sauce. Cover with slices of ham and then Swiss cheese. Pour the remaining soup over the layers, stirring a little to distribute between layers. Sprinkle the stuffing on top, and drizzle butter over stuffing. Cover, and cook on Low for 4 to 6 hours, or 2 to 3 hours on High.