Divorce

Sir/Ma'am I am working as a teacher in a private school. And I'm married to a person for 20 years. And I've two children, one is 17 years and other is 12 years of age. since the first day of marriage I've been continuously tortured by my husband. I know that it is my fault that I should have taken some step when first time I was tortured, but at that time I was only 20 and I thought that I will be a burden on my old parents. and I took no step, I kept myself calm by thinking that all will be good when I will be having child. I had one child than other, but nothing stops until today. And now it is worst ever, he beats me in front of my children. and when any of my children interfere or stops him, than he is beaten very badly like an animal. Not only in front my children but also in front any relative, my father in law also sees everything but he haven't said anything to him ever. And even when we at relatives home he throws his sleepers at my face in front of everyone. Whenever he does that I feel like 'I should suicide', but when I see my children I drop that idea. Since 20 years he is insulting me, playing with my dignity. But now it is worst ever, I just want to live the rest of my life with happiness away from him. please help me. I have wasted 20 crucial years of my life with this person thinking that one day everything will be alright but that never came. Please help me in this matter, what should I do?