Child custody in case of adultry

I am married for 11yrs with a girl child aged 6.4 yrs.me and my husband still living under one roof but we dont talk, no physical relation nor he takes care of my expnses. Its an arranged marriage n i hv got nothing from day one of my marriage. He is least intrsestd in sex, zero financial support, responsibility or care or anything. I am a software engineer by profession worked for 11 yrs n now from past 1 yr am at home bcos he played metal game with me where i couldnt concentrate on my work. I went into depression. From the time of marriage it was like once in a yr he might hv had sexual contact with me. It was that bad. Infact i had my child with medical help but not complicated. I concieved in the initial tests only(thro folicular test) since marriage I have been mentally tortured by my husband. He showed no intrst towards my child too. All expenses n evrything i took care off bcos i was doin good. I kept requesting him for divorce but he wants us to b with him only for society. Infact in 2014 he made an agreement on stamp paper but not notorised saying i can do whtevr i want in my life but will live together for family sake. I hv helped him by supporting him financially. In 2014 I have got mentally and physically engaged with a guy whoz our family frn which my husband got to know with in weeks but from last 3 yrs am goin strong with that other guy. So every time i want to walk out of this marriage he threatens me with this affair. Recently he might hv left some detective bhind me n collected the proofs. His cousin brother has done this on behalf of him. Now his cousin is threating me n my guy about the proofs. He is got photos where v r sitting in car n giving gud bye kiss on cheeks n other photo in public n says they hv got much more proofs which am not aware to what extent. So now my question will i lose my child custody? should i imm move for divorce r if i keep quite n what if he files for divorce b4 me with these proofs. Btw me n my husband v currently live like strangrs n sleep in diffrnt rooms n no physical contact at all.