I completely understand. I have done that for a very long time because of the abuse and the emotional abuse from BPD mother.
I played the "pick me" dance to no avail.
I believed all his crap and a lot of horrible things he said to me. Kept saying to myself If I only did this, or only did that he wouldn't have cheated. For so long, he was the voice inside my head and I would always self doubt myself.
I know that the longer I had NC, it started to get better. I, too, was working a minimum wage job, but got praise from my managers who were a lot younger than me.
In the past 6 months, I've gone through 4 different jobs, getting a better one each time. Throughout this journey, I've met some very kind people who helped build up my self esteem by praising my work and when I had to quit, they didn't want me too telling me how good I was and how nice I was.
I wasn't used to it. I was so used to being put down or having my family just asking me to do things and complaining it wasn't enough.
The doubts will still seep in, but as you go longer without him, your self confidence will start to build up again. I know how difficult and tiring it can be to have to be giving yourself a pep talk to keep you going. It's emotionally exhausting, but it will get to a point that you will start to have self acceptance. You will feel better about yourself.