OP, your post rings a bell with me too.
Like you, my childhood was full of neglect and if my mother wasn't ignoring me, she was hitting me. This started about the age of six and by the time I was 10 things were bad enough that my dad sent me to boarding school. Only he knew nothing about boarding schools and didn't realise how harsh and cold the school was that he'd chosen and I didn't have the words or the courage to tell him. It was wretched and I hated it. I've wondered many times if I'd have been better off as a ward of the state, at least I might have had a bedroom of my own and someone to talk to.
Fast forward, I began serious work on myself in my late 20s and realise getting over and through this stuff is life long work. Early life neglect/trauma rewires your brain and you have to find a way of fixing that. For me, meditation, journaling, physical work, questioning, reading everything I could find on the subject. Lack of trust and realising that if you really want something done, then do it yourself has meant I haven't had therapy or medication and have preferred to figure things out in my own way and it's worked quite well. I'm in my 60s now, in a solid very long term relationship, do a job I love and consider myself sane - result, or what.
I also started Inner Child work, as described in the link below. In that work, you basically do the job of parenting yourself, sort of becoming your own mother, and you do it properly this time. If you have any photos of yourself as a child that helps to focus on the time things happened. You meditate on your younger selves and comfort them. Create scenarios where you meet with your younger self and do something good - brush her hair, buy her some new clothes, take a trip out to a museum and stop off for tea cakes and hot chocolate afterwards, play together on a beach in the sunshine, or just sit and cuddle. It doesn't matter, just do something comforting.
I did the ACEs (Adverse Childhood Experiences) questionnaire and scored 9/10, which is a bit grim, but then I did the resilience questionnaire and found that I'm surprisingly resilient. You might surprise yourself if you do the same. Dropping the idea of being a victim and instead focusing on being resilient has helped me more than anything.
Visualisation helps too. I sometimes wear an imaginary hat, the sort you might buy in Skegness that has a band around it saying 'Kiss me quick' only it says 'Fuck you, pal' to everyone who treated me badly and to all the negative self-talk that used to circle in my mind. I also set up a sort of affirmation that goes 'This is MY mind and I'm in charge here, thank you very much' and that's helped too.
It's been hard work, but it can be done.
https://www.mindful.org/healing-the-child-within/
https://cls.unc.edu/wp-content/uploads/sites/3019/2016/08/From-ACESTOOHIGH-ACES-and-Resilience-questions.pdf