<human>: Can you summarize the given text in a few sentences?

So it all starts around three years ago, when we first met. At first I had just broken up with my ex and I didn't want a serious relationship, so we ere just friends with benefits for a while. Then we started dating, and six months into it I met this girl (I'll call her S), and we kissed a couple times on a casual date at a local park, she was more into it than I was and she invited me over to her place but I refused because it didn't feel right and I just wasn't into it. I actually started talking to her about my gf because I was feeling guilty and ashamed of what I had done.  
 
At that time, my gf and I were not in our best moment, but as time went by I started to realize that she's the one I want to spend my life with, we share so many things, we understand each other in the deepest way and I love her more than anything, I have never felt this way for anyone, and it's been two years since that happen.

I have tried to tell her many times, but everytime I've chickened out and just said that I needed time or that I wanted to break up, because the guilt is haunting me and I don't feel like I deserve her for what I did. 

Turns out that S is one of my gf's friend's ex, and yesterday S told my gf's friend that I am her ex. We never dated, we never talked again or anything, and my gf didn't believe anything and just laughed because it's actually not the first time someone lies about being in a relationship with me. 

I am terrified of telling her, I feel like the chances of her founding out are pretty low but I still don't know if I should tell her. She has  always hated cheaters and I know that this would hurt her more than anything. I fucked up, I know, but I just can't lose her.
<bot>: cheated on my gf two years ago, we have now the perfect relationship but she coult find out and I don't know if I should tell her.