Job, Memory Loss, Discipline Issues, Legal protection?

Guys, I have Juvenile Mioclonic Disorder. I have noticed that my short-term memory has been affected as I age, despite being seizure free for about 6-7 years, thanks to a good balance of medication (Diprovan or Depakote generic, something like that). I do excellent at my work. I work with case loads and I always complete all my caseloads by the deadline. My only recurring problem is that I forget meetings, even when I've been told and when it's on the calendar. I get involved in my work and time passes, and I miss deadlines. I've spoken to my supervisors about my epilepsy concerns and that I'm trying to put in place habits to remind me of meetings, etc...but my supervisor hasn't taken that concern very seriously and has elected to give me written warnings which I feel are making the papertrail to later, fire me based on a collection of "incidents" of forgetting a meeting, etc. The bulk of my work is successfully processing casework, so what I've missed in meetings really hasn't produced a major loss for the company or for myself. What they hired me to do, I'm doing. But, it is company policy and the supervisor is getting peeved that I continue to miss meetings (I'd say I miss 30%, and make 70%). What medical/legal actions can I take to provide myself with some protection? Am I covered by any national legislation (American with Disabilities Act?)? Can I present my supervisor and the department head and any other higherups with documentation that might convince them to be more lenient or accomodating of my situation? I just want to avoid being unfairly disciplined for something that I was born with and which I struggle strongly to avoid intervening in my daily life? What protections exist?