I SOOO know what you are going through. My latest depression was brough on by several things, the death of a good friend, many changes in my personal life AND extreme uncertainty about my job. I was working as an office manager for a group that had extreme growing pains. My job had changed so much that there was barely anything for me to do. I had to keep my job because my kids were in college but all of a sudden my job was killing me. Here are the things that I learned and advise:
1. You are not your job. While you have this job try to find some interests or activities outside of work that interest you.
2. Having a job that you don't have to work at very hard frees up mental space for new things. I went back to school and expanded my skill level. This allowed me to find a new job.
3. If you can manage the money find a career advisor, it was the best money I spent to change my life. My career advisor was more than just that, she supported me emotionally, she really listened to me and what I wanted, she recommended the best therapist I have ever met and she had solid skills and tools that helped me move out of a situation that was killing me.
4. Don't let go of the job you have no matter what until you have a job to go to. Even a bad job gives you an income.
Best of luck, keep us informed.