Sex with my son and pregnancy, leading to unprecedented blackmail

Dear Sir, My name is Ashley and I am a 43 year old divorcee. My divorce reason was due to the abusive nature of my husband towards me and my children fuelled up by alcohol which included routine beatings.It was easy for me to get divorce and life went smooth after that. My children were my life. Two years before, my twin daughters who were 16 at that time died in a road accident.My son and myself were emotionally shattered but somehow we made it through. Right now I live my life for my son and my son live for me.We are always there for each other. Our closeness somehow went to another level and me and my son developed a sexual relationship with each other which is continuing until now. I got pregnant 5 months before which happened because of my carelessness in taking birth control pills regularly as my work life was too hectic.My son is 23 years old now. The gynaecologist I visit is my ex- husband's business partners' wife.She told her husband about me and my son and our sexual relationship. He told this to my ex-husband.My ex-husband is blackmailing me for money on a regular basis and till now I have given him close to 1.5 crore rupees. I left my last company where I was the accounting head and joined a new company in the same position and I am getting an excellent pay package.Along with that, my ancestral property is a lot which is enough for many generations to survive without even working. My ex-husband is asking for half of the wealth and he is telling me that if I don't comply, he will tell the police. He is an evil person in all respect and whoever meet him has that opinion about him. My questions are 1) is my sexual relationship with my son a crime in India? 2) Can we continue having sex? 3) Except the sex part, I am my son's mother in all respects and my son love me back in the same manner. Will the law see the baby we have as my grandchild or my child? 4) is there anything else we need to be concerned about?