<human>: Can you give me a shortened version of the text?

Me and my girlfriend have been dating for 8 months now and things are great. But when we were only dating for about 1 1/2 months things weren't doing so good and we hadn't seen each other in over 3 weeks for reasons I don't remember. I felt things fizzling out so I asked for a break until we saw each other again.

Soon after that, my ex started texting me and she was going through similar things with her boyfriend. We started flirting and it went pretty far but never anything besides sexting. She was telling me that if things didn't work out with my SO then me and her should become FWB. 

I wasn't up for that because at the time I was saving my virginity, but I told her if things didn't work out I'd think about it. But me and my SO had planned to spend the day with each other on the weekend and it was fantastic. I fell in love with her and made me never want to flirt with anyone other than her ever again.

I told my ex what happened and explained that I can't talk to her anymore and she agreed with me. But now that time has passed it has been eating me up inside. I don't want to tell her because I can't imagine life without her.

I don't think telling her would solve anything but hiding this secret is nearly killing me. What should I do reddit?
<bot>: I messed up and now feel horrible about what I did, things are fantastic with my SO now and not sure what to do. I need your help r/relationships. Thank you so much for taking the time to read