Lonely, Old and Disconnected. Can't stand the loneliness and sadness anymore and it's making me a worse, bitter person

Folks, I (31M) have been reading though the posts here and while I see similar patterns to what's going on with me, I don't really see anything that gets my hopes up.

I am a somewhat successful person, in a stable job and in a stable* (will get into later) relationship. This might be the first time in my life where I'm not actively running away from something or putting out fires and there is such a huge void in my life

The problem is: I spent most of my life being someone I now violently dislike: people-pleasing, arrogant, shallow and want to move past that. My girlfriend is supportive but both her and I know that it's a process that can't be done in such a limited context. We have tried in the past and all it did was make me more dependent and make her emotionally burnt out. Not only that, but it added friction and conflict to already frayed aspects of our relationship, parts that were frayed because of my reactivity and inability to open up in the first place.

My history isn't great but it isn't the worst either: I have a distant, self-centered mother (she does her best, but she is trapped by her own mind) and a narcissistic, controlling financially abusive father, who I cut off 3 years ago and am only now able to look at with only sadness and not just hate on top of hate. Sex and sexual connection has always been an issue for me, as I had some unwanted contact as a child and then was pushed into "manhood" with a professional by my father in my mid teens. All of this, coupled with moving around and always being the "weird kid" led me to putting on a mask that I've recently been able to start looking under, and it has revealed a bitter, lonely, scared child underneath. This led to arguing and extreme reactive behavior, actively shutting down when confronted, especially by my girlfriend, which has made it hard to actually change. I always default to defense and anger, as if any further harm to my psyche is just unbearable.

I am at a point where I have been going to therapy for years and improving some aspects of my life, including the violence, rage, reactivity, but I just feel so lonely. Me and my girlfriend have a open relationship and it does take the edge off some things, such as a flaky sex life, a need for independence for both of use. I don't really "use" it because I am scared on failing at sex again, and because I don't want to open up and be vulnerable with anyone else.

I also have come to the realization that I don't have that many friends. While I do have some people I'm able to talk to and connect, there still feels like I put up a screen between us, and there aren't that many people. I used to be a very social person, but trying to reconnect with my old friends from my masked days has mostly led to disappointment and me retreating further inside myself. I feel like my heart is closed and there is so much pain within it and surrounding it that I can't bring myself to open up and face disappointment when I find people boring anymore.

I feel alone, I feel best when I'm alone but I also feel like shit all the time. I see the advice here on going out to talk to people but I just find that so immensely draining and I can't stand another empty conversation. I've been trying ways to go deeper but I'm so numb that I can't even follow though with what I want, because I get disconnected and bored and I just let everything drift off. I feel like asserting myself and proving that I'm not the piece of garbage I feel that I am is all I want to do, so I am barely present overall.

What can I even do? I feel hopeless. I want to open my heart and become more connected to people. I want to be more empathetic, I want to open up, I want to meet people, to love and be loved but I am pessimistic about being able to get out of this. I can't stand crying alone anymore. I can't stand being so closed off that I barely know myself.

What can I do? Has anyone gotten out of this kind of hole? How does one meet people? Am I even able to?

I am in therapy and take antidepressants/anxiety meds, I just know that it's a temporary thing to allow me to feel and process my life and they don't really solve what's deeper.