Losing my family over mistakes I've made

Not enough space here to get everything out, so I'll get the main points and continue on a comment if I can.

My fiancee has broken up with me over the past 2 weeks or so, I've hurt her emotionally too much over the past few years & it's gotten past a point. We have a son together (almost 2), & she has a daughter that she was pregnant with when we met (almost 3). I'm trying desperately to salvage our relationship & dont want to lose any of them in any sense. She is my best friend and I'd dreamed of spending my life with her, & raising our family together.

On to what I did to get where we are now. In the past, I guess I had a problem of letting go, or maybe I was scared, not sure. I had pictures of my ex's saved on my devices, & didnt get rid of them as I should have. I also had an issue with pornography to an extent. I saved all of these pictures & hid them from her instead of deleting them. Just as well, i talked to some of my ex's, nothing explicit, just as friends, but they were trying to cause problems & instead of shutting them down, I just hid it. My fiancee has bad PTSD & issues with self worth. All of these things were a big issue for her. She found them right after we had our son, & while I loved her more than anything, I still hurt her, & it ruined his birth for her, & it's been stuck in her mind permanently.