Want to file a Divorce

I am married for 8 long years have a 7 year kid. Mine was a love marriage. But soon after marriage I came to know all the things that were told to me by my husband were a lie. He was not at all financially settled and we struggled a lot. And now , he has left his job started with a business and he is in a huge loss and debt. Now he harasses me daily for lending money to him , but I don't and out of all these , he also have the habit of betting . My kid is suffering a lot because of this and He makes sure he fills my kid's mind against me , so that I cant leave him. Also , his mother tortures me a lot . Out of all these sickness and family trouble , I met a man and had fallen for him. Had an extra marital affair with him. it lasted for 2 long years and My husband came to know of this. And now he blackmails me , that if i plan to file a divorce , he will sue me instead and charge me a lot of money. Also , he has taken huge amount of money from my Mother as well which he says he will not return.