I'm sorry to hear you're feeling that way OP, I know it all too well. I had a rough childhood where I was essentially property, rather than given any independence to discover myself.
As a teenager almost my entire personality was built on being a victim, and feeling entitled to special treatment because of that. Lots of tantrums, lots of people hurt, no real awareness of myself or the damage I caused at all.
I suffered awfully with mental health issues for years, and then, eventually, I had the mother of all breakdowns. On reflection I think it was more of a breakthrough. For a period of around a year or two, I completely lost myself, or maybe got lost within myself. I was nothing. Not happy nor sad, not enthused or unmotivated, just nothing. Complete autopilot, a robot in the truest sense. No descriptive word was something I could relate to myself in any way, it was all just noise.
And then slowly, I became able to organise the noise. I knew wholeheartedly what I didn't want to be, and stopped convincing myself I was those things. We can truly be our own worst enemy. I started to accept the things I was, neutral as well as good and bad, and made efforts to balance the scales before tipping them to the 'good side'.
I thought religiously about whether I'd want to meet myself, and adjusted my thoughts and behaviours as necessary to achieve that.
I'm not all the way there by any means, but I've achieved my initial goals and moved on to new ones a few times over.
I feel content most of the time, I feel aware of myself, I feel in control of my emotions and how I handle them, I feel confident and sure of myself in everything I choose to do, and in most things I have to do. By contrast of feeling nothing at all, I now feel human, and that has been worth every second of pushing myself.
It wasn't easy by any stretch, but I now feel capable of looking after myself and no longer rely on others to do so, meaning I enjoy it all the more if someone chooses to.
I do have to give credit to a wonderful ex partner whose gentle and persistent approach played a huge part in my acceptance that I wasn't an inherently bad person, and that my 'bad' thoughts didn't define my being.
About a year ago I met someone I'd last known a decade prior, and they said they'd never have believed the difference had they not seen it for themself. That was affirming, but the real tell for me was that I didn't seek or crave the extra validation that someone else could see my progress, because I knew I could. That was the first time I realised I had made progress I was proud of.
I wouldn't say my personality has changed, there are core parts of me which have existed throughout, but I would say that it has developed or evolved. I organise and present myself differently, but I'm the same person I always was.