Hubby has totally changed...I'm scared.?

This is kinda a re-post from yesterday, but my husband of 9 years has suddenly changed. He started becoming violent and controlling about 6 months ago. He started with physical abuse in March. He is 100% not cheating (just to clear that up), he is not American (he was a refugee from Kosovo), he has always been VERY quiet. When I ask him why, he says he doesn't know. We have children and I love him with all of my heart. How/why can a person suddenly change in such a dramatic way? This is killing me! Please help me figure out what to do or what is going on?