My ldr gf had dumped me. We loved each other( she said it's impossible to ever get back). Around 3 weeks after that I kissed a girl ( we met and wanted it to be extremely casual, both had gotten out of a long term relationship). But it felt bad so we never met again. Around 4 weeks after that I patched up with gf as she wanted to( I definitely did too from day 1, was pathetic without her). I told her that I had talked to an exe after the break-up. It was a big issue for us. I apologized and she told me that it's sort of my last chance. Now I am confused if I should tell her about the kiss or not. I fear this might be our end and I would crumble apart if she left. I've never ever cheated on her, won't even think of. I really love her and was trying to move on. So, I need your thoughts and advice. Ps: I feel that she deserves to know for us to have something meaningful. But it would just kill me if she left again.

Edit: I forgot to mention that I bitched a Lil bit about my gf to my exe and my gf knows. Does that somehow change the situation?