Girl Needs Advice - I'm Engaged, But I Am Having the Greatest S*x of My Life With Someone

I have never felt like a woman before until last year. I am 27 years and I have always known one man all my life, but last year. We passed out from youth service and my boss hosted a dinner party for all the Youth Corp members that worked at the company; we all came drank and my childhood friend that I invited from abuja to Lagos came, a guy, we do have feelings for each other but I am engaged already. My fiancé couldn't make it because he said it's a childish stuff, that he is too big being around children. Well l left him, though I was angry because his presence would have made a difference.
 This my childhood friend gave me 3 years gap, he is working in his father's company. That night when I escorted him to his hotel room, he started professing his love for me. Honestly, before I knew what was happening he undressed me with his teeth, took me to the bathroom showered me, and made love to me in the bathtub. I couldn't even say no again. I have never experienced such a thing in my life.
 My fiancé is always saying I should not live a wayward life, that s*x is for married people and the purpose of it is to get children. I believed him a lot because once he is up, he puts his penis in me, pushes in and out and gets down and ask for food.
 He has never asked me what size of bra and pant I wear. He made me have this mindset that s*x is just to get children, but after last year incident, I knew better.
 My childhood friend has been coming to visit me, he makes me go crazy anytime he is in bed with me. He buys me bras, pants, cooks for me . Once my fiancé just gets up all he ask me is to spread my legs for him. I keep asking him if s*x is for married people why can't he wait till we are married. But, he has not answered me that particular question.
 My problem now is my fiancé is coming by Easter to ask for my hand in marriage and I feel so scared that I will end up cheating on him. What do I do?  This my childhood friend told me not to break his heart, that he has loved me from childhood. I am getting so attached to him. I am so scared because I am in a fix too. What should I do? My fiancé is 40years and my childhood friend is 30 years old.
 
From anonymous worried woman.