I've had with 2 people...help!?

Hi, so I am a christian and believe in only having one partner in your life time. My fiance and I lost our virginity to each other before we split up, but we were fine with that because we knew we'd be the only ones the other would sleep with, but then we broke up...we are now back together. Unfortunately during our 6 month period being apart I saw someone else, and thought I was in love with him, and had with him. I have absolutely no idea why I did this, and now I can't deal with my mistake. My fiance knows and is ok with it, but I am not. i have considered physically hurting myself to get rid of this pain. I feel like a tramp, a , a slut, and I can't make these feelings go away. I cannot believe what I have done, and there's no way to take it back. Can anyone please help me out, before I end up in the psych ward of a hospital...I'm going to hell because of this.