What can l do,I'm afraid of my wife.?

when my wife started misbehaving,l was planing to divorce her but before divorce,l started to meet a lady out in town until she got pregnant.latter,we were sat down for counseling.my wife went back to her senses and good change in behavior was observed.This lady gave birth to a girl child now 1year old.Privately l take care of this child but my wife is not aware of anything.l have been with my wife for 18years.lam afraid to disclose to her of this problem because l know she would find someone to revenge as she has always told me.moreover she likes talking too much.if l keep on hiding from her in case the child dies l as the father to the child certainly l will be called to witness and hiding will be no more. Am just supposing eh!