Older cat meowing and howling at night. Had him to the vets no blood test, say he is in good health for 16.5 years old. Told to try melitonin, worked first couple of nights. Back to meowing the same time 2am . Please help, I need sleep this has been going on for a year and a half. What can I give him. Tried lights on, play before bedtime, melitonin