I am worried about my 11 year old male cat. He seems to be acting rather lethargic compared to his usual. I brought him to the vet and they tested him for diabetes, kidney, liver, and thyroid problems. His levels were all normal. He just doesn't seem to be himself. He is still 17 pounds but when I run by hand down his back I can feel the little bumps on his spine and he just looks a little off. Nothing abnormal in the litterbox. However, I have notice he has been vomiting occasionally. Is this just normal old age? He acts so much older than Oogie and they are practically the same age...maybe males age faster than females? Anyone have any ideas? Anything you think would perk him up?