My cat is about 9 and he acts normally like he always does. But when I got back from being at school for 3 months, he seemed a little skinnier. I can feel his spine and hip bones and it makes me worried. Is it because of separation anxiety? Because he also peed places he shouldn't while I was gone. Or could it be something with his thyroid? I'm just terrified to take him to the vet in fear of the worst.