I Decieved an angel for 9 yrs,now the bubble is about to burst

I'm Chris,and I have been married to an angel,a God-sent woman for the past 9yrs. Toun,my wife is an example of a virtuos woman.its not like we don't have our differences or misunderstandings,but she always has a way of handling them maturely. Really ,I have offended her. I can't tell what came over me when I cheated on her. Funny enough,I did that in the very first year we got married. Just two weeks after our honeymoon, I ran into an old lady friend of mine. She was looking prettier than she used to,with all the curves in the right places. We exchanged numbers,and before one could say ..chris watch out.,we had slept together. I was on my way to d office two months later,when Nneka,my lady friend sent me a text msg,asking me to call her back. I did that immediately only to hear what I never expected.Nneka had missed her period. I had to abandon work that day and pay Nneka an unscheduled visit. I tried to convince her to get rid of the pregnancy but it all fell on deaf ears. Her reason? She was once married for 3yrs and had no issue in the marriage,although that wasn't the reason for her marriage break up,but she had always longed to have a child of her own because time wasn't really on her side agewise. Her explanation also fell on my own deaf ears because I was considering my wife. What would I tell her? That I couldn't even wait for the marriage to progress a little before bringiing out the oliver twist in me? Well,I had to let Nneka be,but I made her promise me that she won't show up later in future to disturb my famiily with the baby,and she agreed. And she stuck to her words. But I just found myself going back to her regularly,not because of her but because of my son she bore for me. The little man looks exactly like me. I don't need a DNA test to confirm. The problem now is that I miss my son so much and would like to spend evry minute with him,Toun my wife has 4 girls for me. I need a heir,or rather I have a secret heir that I would love around me. Pls advice me ,what do I do? Do I break the news to my loving wife and bring in my son before she gets the info from elsewhere or groom my secret heir outside?