Ginny,
Under ADA, employers with 15 or more employees must make reasonable accommodations. The Job Accommodation Network (JAN) is part of the federal Dept. of Labor. They have a set of fact sheets; and one for people with cognitive impairment, includes accommodations to need help the employee with concentration, maintaining stamina, etc. (and many others). You can call JAN at (800) 526-7234. They will work with you over the telephone. Or check
www.dol.gov/odep/pubs/fact/jan.htm
I don't know if your employer can get out of legal action because you haven't been there a year, but I think JAN would know that, and also might negotiate a plan with your employer.
Good luck. - Carol