My cat is ripping out his fur

Hi,
I've had Shadow for almost 6 years now. He's a fairly shy cat but has slowly come around. Since the day that I got him he's been ripping out his fur. But never to the degree that he has just recently. I moved back home about a year and a half ago so he's had to adjust. He's seemed fine. Gets along with my parents and loves playing with my dad. I left this weekend and Shadow was fine. I got back tonight and just noticed that he has this huge bald spot on his back at the base of his tail. I'm really worried. I don't know what to do. Does anyone has any ideas?
Please help.
Thank you
Ro

Either it's stress from your having left him for the wknd, or else he's allergic to something in the environment (or the food he was given while you were gone?). If it's an allergy, the vet can give you something to help (usually corticosteroid cream), but if it's stress, you could try one of the Bach remedies for a short time at home til he's feeling more secure. It's very hard on cats to suddenly be moved to new places for a few days, and best if someone comes in to feed them instead.