Embarrassed by job, struggling with self-esteem

I'm 28F and I've had the same job since I was 23 in an office as pretty much a glorified receptionist. I started with another job, but was assigned other duties along with my original job when the company downsized. I don't feel valued or important at work.

I'm really embarrassed about my job and lack of success. Most of my friends have better jobs and are more successful than I am. I'm actually embarrassed to hang out with people sometimes because of this. Even though careers rarely come up, I know that my friends and acquaintances are better than me. I feel like I'm not on their level.

Nothing has worked out for me. I have 2 degrees, Bachelor's and Master's and have failed at finding jobs in either field. I've written a book and failed to get a literary agent to have it published. As of now, I'm just a self-published author working a crappy desk job with no future.

Please don't respond with something along the lines of "look at what you've done already", or "you've done better than a lot of other people". That doesn't help and I know, but it's not good enough for me. I've had issues with this for years and nothing has helped me get past it. I've done online therapy once and it did nothing but raise my credit card bill.

I don't know what to do anymore, nothing makes me feel better about myself.