I definitely know where you're coming from. I graduated college and did not get a job and actually waited tables with a bachelor's degree (and it wasn't Philosophy or History, it was engineering!). I found out years later I suffer from social anxiety. I was terrible at interviews and I knew I didn't want a desk job, so I got the jobs that were easy to get. But, even then, I always felt like an imposter, like someday the boss would come to me and ask me into his office and fire me. But, they weren't doing that. They actually really liked me for the most part, but I wouldn't listen to any of the praise, only the criticism that I (mostly) imagined.
I went from job to job until I found one that was bearable. I agree with the person who said the low paying jobs treat you like crap because they can. The only jobs I've been treated like crap have been the jobs that were easy to get and didn't require a college degree. The higher up you climb the career ladder, the more respect you will get and the better you will be treated.
Ever since I found my bearable job, I've been able to stay in a similar industry, moving up and sideways and up and sideways a bit more, and up to a master's degree and now I'm here. I wouldn't say it's my favorite job, but it's the first actual engineering position I've had, which makes me feel so good. And in the back of my mind, I still have that fear that people are talking behind my back about how terrible I am, but I don't listen. And, I make sure to hear the people that are praising my work and know deep down that I will not be fired for not doing a good job.
For me, the best thing has been meditation. It is hard, and I don't do it as regularly as I should. But, keep at it and you will see a difference. I find I'm less cranky, have more energy, and am able to socialize easier when I've been meditating. BTW, I learned to meditate in yoga. If you have a good yoga instructor, they will incorporate it into class. Good luck!