Loving an avoidant can hurt

Please excuse the long post. I am struggling with my decision to break up with my girlfriend. We had been together for 2.5 years and there were way more good times than bad, though there were a couple of times where things did get bad. We did sometimes learn from those mistakes, heal and move on, but things took some unfortunate turns last year and now this year. Both of left abusive relationships. It took me months of counseling and talking to people to feel "normal" enough to date. We met and instantly clicked, though we were both cautious and patient with the relationship, owing to our past. I bonded with her children, though mine were a bit harder to crack. We supported each of us equally. Christmas of 2019 she broke down and couldn't cope, pushed me and everyone away. I know she gets issues in winter and being shut out was hard for me but we worked on that. At the time she was overwhelmed. She feels like she failed her kids in her past relationship and has been trying to make them happy to offset that guilt. Holidays and birthdays being a whirlwind effort to please. I was always there hand in hand. At the same time she has been feeling like the stress is taking a toll on her body and has become concerned with how she looks, though she is and always will be beautiful to me. My mom was diagnosed with cancer in February of 2020. I had quit smoking not long after our relationship started and had been doing well. Unfortunately, I fell off the bandwagon and began a period of feeling very down. My ex girlfriend was the one who got me to talk to my mom again. I had been estranged from her for years. A problem I myself couldn't bring myself to solve. As time went on, she began to resent my efforts to help. Insisting that she could do it all herself. I had no doubt about that, though it was if she needed to prove it more to herself as she tried to make up for her feelings of failure. By spring my girlfriend had become increasingly distant towards me. Sometimes things were amazing and other times she seemed nearly always angry. One day I found out she was on dating apps and I confronted her. She said she was just talking and I believe her only because she has so little free time and the pandemic of course. My mom died and she supported me, I regained trust and we moved forward. This past fall and Christmas was unusually unsettled for her. Work and the kids were hard and with the holidays approaching, she became more angry if I raised any issue or concern. More frequently snapping at me. I could always help her manage those stresses by helping, listening and loving. But the less we saw each other as she wanted space, the less she got those things to help manage her stress. Unfortunately I made another discovery that she had been speaking to another man outside of those dating apps and didn't disclose that at the time we sorted it out before. Again, I feel her embarrassment and remorse probably kept her from acknowledging that too and so those feelings of guilt began to fester more. I don't know that anything physical happened but it brought back a world of hurt. She did stop talking to him not long after my mother passed. I then began to feel more and more emotionally unsecure in the relationship. When I sought reassurance, she began to pull away saying I was too needy. But it all kept coming back as a feedback loop. The more she pulled away, the more I pushed for a connection. I knew that when we were together things were great, but I just couldn't give her the space she needed to be her. When she canceled plans we had made for a weeknight sleepover I was unhappy. She didn't want to apologize and felt she deserved the space she asked for and I agreed. But I didn't like how she handled it. By the end of the week my emotions got the best if me and I broke up with her. Now all I feel is regret is self loathing like I was partly to blame for the breakup. She won't speak to me, but her one friend is and has been acting as a kind of go between. I appreciate her friend talking to me. Her and I were acquaintances before the relationship. I have forgiven my ex girlfriend for what ever happened and I would like us to get help to try and slowly get back together but I fear its 99% over. I have struggled with sleep since then and am working hard to bring myself out of this funk. I have started exercising again (running, weights), trying to keep myself moving, but I can't shake this feeling of regret. I wish that there was something I could say to her that would give me hope that something would work out or some sort of closure that its over for sure. I know I may never get that from her. I am thankful for the time together, though desperately sad at the loss of what was going to be a family of 7. I miss her children. I miss all of them. I feel so alone. I just dropped of my boys for their week with their mom. 7 days of only work and whatever I can do to keep myself distracted.