Help with my dog please?!?!?

My yorkie (male) is about nine years old and lately has been behaving oddly. Having come from a neglectful home, he's always been a bit protective, though lately if you try getting near my mom or if someone else tries to get near me while we are in our rooms he will bark and growl, no biting or teeth bearing but he behaves aggressively. He is normally an amazingly sweet dog and I'm not sure if it's his vision. Thank you!