Disclosing Mental Illness at Work & Building Support Systems

I had good relationships with people at work. I was given projects and basically set my own schedule and due dates for the most part. I had a lot of work and a lot of people who "liked my work." I got the best reviews you could get.
Then it all fell apart and I broke. Things from the past that knocked down walls and came roaring out like a freight train. I ended up being out of work on FMLA for the max time allowed.
When I got back they had papers all ready to get rid of me. I came back before they could. Yet when I got back projects disappeared. I had new rules regarding attendance. I had to claim ADA to protect myself.
During all this time I had a supervisor who knew everything. We were friends. She seemed to care and tried to support me but then she got promoted and stabbed me in the back. So do all the people who thought my work was wonderful. I suddenly got a meets satisfaction review. They changed my managers around (without telling me) and I ended up in a group that was let go. Did anyone try to help me? No. Did my "friend" help me? no. Had another friend outside of work who dropped me.
So my thought is don't tell. People can't be trusted. They lie. They do mean things. There is no support. No help. No life. I really have no idea what happened. I don't know what everyone turned their backs on me.
If you have a job, keep your mouth shut. Tell no one. Avoid medical leave if at all possible. Once you take leave, you are gone. Also keep in mind even though they are not supposed to know, they can see what you spend on medical and it factors into who they keep.
People can't be trusted. All the problems came from people doing bad things. Trust no one.

I wish this hadn't been posted so long ago. I am about to start another year at my job as a special ed teacher. I love my students but have been shit on so bad by similar experiences as yours.
I worked very hard to get my supervisors license and was basically the shining star in our program. One day, I just fell apaprt and had to do a small stay in a facility. I, like you, thought my supervisor was a great friend. I told only her. All of the sudden, I came back and everyone knew. I am now looked at like a crazy. I have been passed up for five positions. My reviews suck. I have been told I can't get along with people, etc. It's awful. People may say one thing about those with mental illness when a celebrity kills themselves or something but when it is possible that that person may be in charge of something in their building, it is a totally different story.