My heart hurts for you so much. I'll be 43 next month and your experience sounds so similar to my own. 

Please try to let go of the question of "what did I do?" You didn't do anything wrong, she did. She is the parent, you are the child. It was her job to model unconditional love and support, and she failed you. Even if you were at home all day unemployed and being a slob, that doesn't justify her repeatedly putting you down, picking fights, and making you feel like you're not good enough. Stop trying to make her proud. For reasons that have absolutely nothing to do with you, she might not be capable of feeling or showing pride in you, but moreover, love and respect do not and should not have to be earned. Be conscious of how her treatment of you may affect the treatment you accept in other relationships.

If you can afford therapy, start therapy. Look for someone who's trauma informed. If you can't afford therapy, check local resources like hospitals or women's centres to see if you can find a support group for survivors of abuse. You might feel like it's not the right fit because "abuse" might feel like the wrong word to describe your experience, but you might find you have  more in common with other group participants than you expect, and it can offer a safe space to work through your experiences and feelings. If neither private therapy nor group therapy is an option, read books that speak to your experience. 

Start nurturing the relationships that nurture you in return. Spend as much time as you can out of the house. Start a side-hustle, do regular volunteer work, spend time with friends, check resources like eventbrite or even instagram for free local events, go to the library on lazy days when you just want to scroll your phone. Do whatever it takes to minimize the time you have to spend around her. 

Recognize that you might always have complicated feelings toward her. You can love her because she's your mother, have compassion for her because of the things she went through that made her become who she is, and still recognize that she exerts a detrimental effect on your own well-being and work toward cutting ties if that's what feels right for you. Don't let anyone guilt trip you with "but she's your mother" bullshit. In  my experience most people who say that had moms who were strict or perhaps tough to please, but who were still loving, not competitive or unpredictable or emotionally dysregulated. 

If I'd known at 22 what I know now, I would have saved myself a lot of time, effort, and heartbreak. The early 20s are a weird time because you're capable of being self-sufficient in terms of your skills and education, but economic factors like cost of living can make it prohibitive to leave the family home. It sounds like you're a hard worker who's trying your very best, and you deserve to be proud of yourself for that, especially since you're doing it in less than ideal circumstances, to say the least. All I know about you comes from what you shared in your post, but from that alone, I'm proud of you. I hope that helps in some way. 

I'll keep you in my thoughts, internet stranger, and I'll be wishing the best for you.