How do I get past my breakup after 13 years.

Hello, it's been about a month since I have talked to my ex. She essentially said this needed to be done and she had detached years ago. The backstory is, when I was in high school. My parents had actually gained custody of her. Due to her awful childhood and the life she had. So around 16 years old. She started living with me. In the same room. This created a bad case of co dependency. As I aged through my teen years. I wanted to see and meet other girls while she lived with me. And yes while dating. I understand now, her being thrown into my life like this interrupted my growth as a teenager. And it interrupted hers. We have been together for 13 years side by side. Throughout this time. I had put her through a lot. Texting women while we were dating, some manipulation and all sorts of things. When I hit about 20 or so. I started to realize some of the things I was doing were wrong. But I still didn't quite treat her the best. We always went back and forth on what we were. Partners? fwb? Roommates? We typically would just kinda exist in the same house together. While still being intimate at times. But once I thought I met a girl, it would end. I never hooked up with anyone, or did anything sexual. It was usually just talking. This leads me to when I was about 25. We moved into an apartment together, tried to make things work out. I had stopped texting other people. Started to realize what I had. We ended up getting two adorable dogs and things started to come together. Or so I thought. Throughout the two years living together we found we had differences in living standards and cleanliness. So we would often argue about it sometimes. I did forget to mention. I would get upset when she was home late. Even though she literally had no control over it. I was always worried when she was gone. Etc etc. Essentially I limited her freedom. At least that's how I see it. Some days went great and we got along. And some days just sucked. Fast forward 2 years. She files bankruptcy. Decides I need to go, also because I couldn't have my income at her apartment while it was happening. I end up at my parents. And it's where I am today. I did try to get my own apartment. But according to my therapist I have severe adjustment anxiety. So when I tried to stay at the apartment by myself. I just had a panic attack. Packed up my whole place in one day and went back to my parents. Pathetic. But, I'm learning to accept it and how to cope. Eventually me and my ex sat down and said let's give this one last shot. And give it everything. This was when I went to therapy. I said I never would. But it was worth it to me. I started visiting her once a week. To allow her space and freedom. We would go places occasionally. But due to us both having financial issues. Our options were limited. Especially due to the area. But I tried to make the best of it. I started listening to her. Allowing her to be herself. Not being so damn hard on her for her cleanliness. I knew due to her past. Yea she's gonna have other trauma that hinders this. I had helped with finances when I could. The dogs and things like that. Went to the park for walks. Simple but spending some time together. Slowly I really started to feel what I would call true love. I stopped being a prick. I started to see her for who she was. And I really enjoyed it. It wasn't perfect. But it was an upgrade from years ago. 5 months go by. We had went to couples therapy a few times. I thought it helped quite a bit. She started missing appointments due to her schedule. Soon things started to become stagnant. One day I went over to her place. Pretty happy. Did some things for her I really put some thought into and when she got home. Something was off. She was on her phone quite a bit. Turns out she had started talking to people online. Later that evening. She gets out of the shower and confesses to me she was embarrassed and ashamed of some stuff exchanged in a chat with a random guy. I guess just flirting. Idk. I pretty much said if she was taking this rebuilding of our relationship seriously she wouldn't have been online flirting. Or looking for attention. Whatever it was. That night was the last night we were together. We agreed to end it. For some reason , I felt nothing. No sadness when we agreed. Nothing. We both just go to sleep. She had cried that night. I think more about being ashamed than the actual break up. I'm not sure. But I essentially realized what had just happened when I woke up. I broke down into tears. She pretty much just emotionally shut off. And I don't think she could deal with me. The last thing I remember is her watching me leave. The last thing I said was " thank you for giving me a final shot at us" and I haven't saw her in about a month now. She lives like 10 minutes away so it doesn't help. I haven't gotten to see my dogs because it hurts to much. I know I had vague details. But the main point is. I was preparing to marry her. I developed feelings for her I didn't have most of the time in the past. Our life and relationship was messy. I had only been with her. And she had only been with me. I have great insecurities sexually due to a traumatic experience I had when I was younger. This leaves me with a weird possessive issue. Which is why I think I got upset when she was out late. All of that aside. The amount of shame and regret I have is insane. This woman. Who for most of the years I never put effort into. Was such a beautiful person. And I can't stop thinking about it. She was everything alot of people aren't today. I understand I was an asshole. I understand I don't deserve her. But what I cannot get past. Is why she allowed me to build us back up. And 5 months later. Agree to instantly end it. I have a lot to work on. I have a lot of reflection to do. But, after it's all said and done. I miss her truly. More than anything. I cannot stop thinking of her with another man. I can't stop thinking of what could have been. I cannot stop thinking about will she come back. There's a lot of details to this relationship. It's very complex. But she was my best friend. And I did love her. So fucking much. We used to blame it on co dependency. I don't miss her comfort. I miss her smile. Her jokes. I miss everything that was quirky about her. I want nothing than to make up for being a shitty partner for so long. I genuinely understand I fucked up. But, is there any others who can share a similar experience? I don't think she will come back. The last message to her I simply said the best apology I can offer is silence. So I haven't spoken to her since. I want to respect her privacy. And her healing. I mentioned I had no expectations and I understand she may not have the best memories of me. I know it was my fault I lost her. But at the same time. I know she's happier probably even now without me. I'm so scared of learning who she may be or become. Even though I don't talk to her. She has ties to my family. That exists today. I am moving out of my parents in a few weeks. I know I'll have a hard time due to my anxiety. But I'll get by. I've been going to the gym, reconnecting with old friends and family members. And various things like that. I got rid of my socials etc. I have no interest at all in talking to women. Not for sexual reasons. Not for any reason other than support as a friend. I want to be better. I want to become happy within myself. I never want to treat someone this way again. I'm learning, I am self aware. And I am trying my best to move on. I will always hope it's her on the other side asking for me to come over so we can fix it. But deep down I know she's gone. My fear is I guess. I'll hear something that hurts me. Especially due to my insecurities. A man making her feel a way I never did. It fucking hurts so bad. I understand I had my chance. But how in the world can I move past this. I can accept she wants to move on. But how do I get these damn thoughts out of my head. It's a constant cycle. I fear she will grow to hate me. Even though I have no intentions of seeing her again. Like, why do I care if I don't want to see her again? I would drop literally anything to fix this. But, I think I've put the final nail in the coffin and she's on her way to new things. After 13 years. It's very hard to accept everything. The fact that it ended so fast. We never really sat down and gave each other closure. The following day she had talked to that guy. Apparently she started sending pics. "I'll spare you the details" she said. I heard this while I was at work. Had a panic attack and stormed out the door. Once again. I feel inadequate as a man. My biggest fear. I do feel betrayed in a way. But I also can't blame her. I just don't understand why she agreed to work on us only for everything to end this way. Revenge? Lust? Attention? I feel the truth will fuck me up. I fear she's with someone right now as I type this. Even though it's been a month. I don't know. I'm just asking for advice I guess. Please don't comment to be an asshole. Trust me. I know what I lost. I know why. But how can I better myself and move forward. How can I get passed these thoughts. Thanks.