I have a 6-month-old domestic shorthair cat. I adopted him around beginning to mid-October. He was very skittish at first, and we would run even if someone is 10 feet away from him. As of today, he has gotten more comfortable and comes up to me and my family. He does like to tear up curtains and chew on everything even though he has a scratching post, he likes to be petted and roughly scratched behind the ears, however, yesterday and today has been a little different. He started chasing his tail with his ears flattened back, trying to dig his claws into people's hands and bite softly (even though it's half-hearted), and I even noticed that he attacks air. On top of all of this, he slightly lost interest in playing fetch, even though this is one of his favorite games, one of his eyes appear to be watery a little, and his third eye is kind of visible in the corners of both eyes, even when he's not sleeping. He is my only cat, and I think he would benefit from having a playmate. Is he okay? How do I know when he needs a friend?