Well, although the ADA does cover for bipolar, I find that at my company that doesn't matter. Bipolar is an "excuse" for people like me....? So, becareful about disclosing before you do. I was naive to think if I disclosed it would help them understand. Instead it made it worse. I'm also reprimanded a lot for mistakes and problems I have that are a direct result of my bipolar.
My one advice is keep track of everything. Print out e-mails or memos that show how you're treated, especially if you ask for help and they deny you.
Good luck.