Custody of my child

I am 36 years old. As my wife abuses me psychologically, I got forced to leave my house. Now I am living separately from my wife. It has been two months since she took away my 4 year old child after an intense quarrel and kept him in her house with my mother-in- law. She continued to go to work after leaving my child in her faraway home. The mother - in- law is keen to keep the child there. She was not ready to show my child to me these two months. My wife visits my child on some weekends. She is too lazy and uninterested to visit him on some weekends. My child is now in the evil clutch of my mother - in - law. I have more than enough money and status in the society to give a decent education and life to my child. I am not an alcoholic or drug addict. I am ethical and educated. As it is not possible for me to give a psychologically healthy life to my child in the presence of a wife who tries to find fault with anything I do, I want to live separately and file for the custody of my child. As I am not sure whether my wife will agree for a mutual divorce,I want to know how I can file for the custody of my child and visitation rights without filing for divorce.