my cat is 3 yrs old and has been healthy up untill a week ago. He's was real active until yesterday its like he went downhill all of a sudden. He eats lots, and drinks and throws up at least 3 times every few days but he is losing weight badly. He was 10 pounds but is down to 5 pounds in a week. Would he have a tape worm or is it more serious. He has had all shots, and is an inside cat.