Adultery and child custody

Hello I m 32,male, a software engineer by passion and profession. We got married in 2008. We have a son 7 years old. We lived in a rented house far from my parents. Everything goin fine for a few years then suddenly i noticed my wife some suspicious activities i.e. unknown phone calls which she hided from me when asked, became aggressive for unknown reason frequently etc. She always wanted to go back to her home. After all i was heavily confused and very frustrated in all her doings. Once she took some sleeping tablets (only 3 to 4 of 0.5mg, i discovered later) and repeatedly saying that she would go home or she would take some more severe steps than this . I begged her, but finally she leaved and went to her hometown with our child. I repeatedly tried to make her feel for me again and come back at least for the sake of our son. But she ignored every attempt from my side and from my parents side also. Later i found her again some suspicious relationships with an unknown guy. I got information about their frequent meeting from a few convenient source of people (her neighbors etc..). I took it as a normal friendship between them...but few days earlier i met my son ..he looked very upset and frightened. I asked him. He revealed that her mother has a boyfriend. That boyfriend comes to their home often at late night when everyone is sleeping and start making love with her mother. After making love both sleep together for sometime and he goes back before dawn. It happens very often now a days in front of his eyes (our son, as he sleeps on the same bed..he assumes sleeping..and he was promised not to reveal anything to anyone)..After hearing all these..I am broken..feel very low...i feel for my son..much worried about our child. What i do now.. Is anyone there to listen to me and to my child..we both feel very child is asking me to take him away from his mother's home. He is now studying there. Earlier when my wife leaved for her hometown, My wife, my father in law, my mother in law all planned and they gave our child admission to a nearby school without my consent....lastly.. i recorded the whole conversation with my son regarding this night activities of my wife and that unknown guy...yes i have the saved audio recording with me.