Story: I Betrayed the one I once called love

All my life I have grown to love my fiance,Ikenna. We have known each other for 7 years, and he proposed to me on my 26th birthday. I never thought I would gradually develop feelings for someone else or is this what closeness to the opposite sex does?

I have worked with Joel for 18 months, he encouraged me to work hard to become a better woman. We became close friends that I even introduced him to Ikenna.
Ikenna never had problems regarding my friendship with Joel, he trusted me with his heart because I had earned the trust after these years of knowing him. Ikenna felt I was in safe hands with Joel because he already had a serious relationship and we all talked about it during our group dates. I had met the girl in question on two occassions.
My relationship with Joel grew even closer, I liked his personality and began to feel jealous when I hear him talk on phone with his girlfriend. I compared my phone conversations with Ikenna to Joel, Joel was cool. I opened up to Joel about everything going on with my relationship and he advised me on how to handle issues.
Soon my discussion with Joel grew to an advanced level, we discussed how we made love to our partners. I began to imagine how good Joel would be. I was getting crazy about Joel, not because I was in love with him but I wanted to explore what he had told me about sexual pleasure.
I didn't stop comparing Ikenna to Joel that it made me have issues in my relationship. I still went to the same Joel to tell him everything. Joel was amazed and consoled me that I could have him if I wanted to, it didn't stop there, we made love in his office. I felt guilty but could not stop what I had already started, Joel was good at it.
Ikenna did notice changes in my behavior but I made up excuses that I was having problems at the office. He tried to make me happy whenever I came around him but I was only interested in my adventure. Fortunately for me Ikenna told me he would be travelling for a two months, his company had sent him to do a course. I was happy because it would give me time for my adventure, I had planned to end it all with Joel before his return.
My little adventure got to its peak as  soon as Ikenna left town, I spent most nights at Joel's place, it was good fun and crazy too. Nemesis decided to catch up with me a month after Ikenna left town, I became pregnant with Joel's child, I got confused as this was the fruit of my little adventure. I have only known Joel for 18 months, Ikenna 7 years. I loved Ikenna more but loved Joel's  bedroom skills. Joel was mad when he found out and suggested I get rid of the pregnancy. How could I have done such again? I have terminated 5 pregnancies for Ikenna in the past and the doctor had warned me against it if another one occured.
Joel and I became enemies when I told him I couldn't do anything about it, now am stuck here with his child. I thought I was exploring a new world with king of the bedroom. How do I explain this to Ikenna on his arrival that am with Joel's child? I betrayed his love and trust.