I felt very much the same when I was 21. I had a job but felt like I was working into the ground so looked for another in a quick space of time. I've been working since I was 17, had a fairly good income but felt like I was unhappy, had barely any friends and no real relationships.
I'm 27 now and can honestly say I STILL have no idea what I want to do with my life, so I've decided recently to quit my job and to travel for around 6 months. I've realised I should've done this when I was younger, as I've talked to numerous people who said it does huge benefit for yourself and makes you look at like in a different perspective.
This might be a good thing for you to explore, I know anxiety doesn't help, but I have that too and I'm trying my best to overcome it! I hope things get better for you in the future