We're going through almost the exact same thing with our 17 year old cat. He eats at least six times a day, uses the litter box normally and drinks plenty of water. He keeps losing weight. The vet has done blood work and says no sign of cancer. He yowls randomly but mostly from about 4 am until someone gets up and feeds him. Could it be a tape worm? Both of our cats had fleas last summer but our other cat is going to turn into a fatty because she keeps trying to eat all the extra food we're feeding him. We have no idea what to do.