I know how you feel. I started my career as a programmer in a good company but I felt like you described: anxious, burnout and overwhelmed.
Quitting is not the answer. You would probably face the same situation in your next job. It's mostly how WE perceive the world around us.
Seek professional help if you can afford it. These things worked for me that I suggest you try right a way:
* Read/listen a good book (how to stop worrying and start living, or similar self-help books) * Eat and sleep well, exercise. There are a lot of internet resources on this.
Good luck.