should I come clean

Fast forward a few years and he and his wife have split and I was in a serious long term relationship. We run into one another one day, with a group of friends, and spend the whole day catching up. By the end of the night, we are back at his place. 

We spilled the beans about everything to one another. His failed marriage, and what went wrong, and my relationship (he knows my spouse), how I'm ready to get married and have kids and my spouse who is in his 30s keeps stalling. It's at this point i confide in him that when we were teens, I had this huge crush on him but I never acted on it because I didn't want to ruin the friendship. And then we had that one night where we did sleep together, and it was amazing. He admitted that he had always had a thing for me when we were teens but didn't dare act on it, and that even since he's been married, he thought about me a lot. 

I don't know if it was the alcohol or if it was the 16 year old me talking, but before I knew it, I was telling him how unhappy I was and how sick of living in a life where I was putting my hopes and dreams on hold. I hadn't even come clean about that to my best friends and here I was confiding in a guy I hadn't spoken to in probably 10 years. 

Next thing I knew, we were all over each other. 

I didn't even feel guilty about sleeping with him the next morning when I went home. My boyfriend didn't even notice me come home. He never once called to see where I was, if I was ok, it was like he didn't care. That's when I knew it was over. 

I packed and left him the next day. And I sent the other guy a message to tell him that I left my spouse but didn't want him to think it has to do with him. He opened my eyes to the relationship and where it was heading, but I was leaving my spouse and I didn't want him to think it was for him. The other guy didn't respond to my message. 

After about two months, my ex and I were still talking on a daily basis since the break up, and even hung out in group functions on weekends often since we had the same friends, and I hadn't spoken to the other guy since the night of our hook up. My ex and I decided to try it again. We still loved one another but I was nervous since I didn't know if he changed his mind about marriage and kids. 

It's been 2 years since all that's happened and my ex and I are back together, get along better than we ever did, and we are getting married very soon. 

The other guy got back with his wife, and when we see each other we make small talk, but we pretend that night never happened. 

I'm just wondering if I should tell my fiancé about that night. I don't feel guilty since we were in a bad place, we didn't spend time together, we didn't speak to each other and we wanted other things. We were more like roommates. So I don't feel bad because it gave me the courage to walk away, and made him open his eyes to what he wanted and made our relationship better than it's ever been. But I don't want to start a marriage with this secret. But I'm worried once he finds out, he will leave me because I don't think he be able to get over it. And I don't want to lose him.