Under the Americans wth Disabilities act , your employer has to make reasonable accomodations for your disability. You cannot be terminated on account of your disability.

First, not all disabilities qualify under the act. There is no hard and fast rule, as for what is and is not a disability under the act... it is a case by case analysis.

Given what yuou have told me, i think you would qualify, and yoru employer must modify your scheduel to fit your disability

Here is an excerpt from the EEOC website:

An individual with a disability is a person who:

• Has a physical or mental impairment that substantially limits one or more major life activities;
• Has a record of such an impairment; or
• Is regarded as having such an impairment.

A qualified employee or applicant with a disability is an individual who, with or without reasonable accommodation, can perform the essential functions of the job in question. Reasonable accommodation may include, but is not limited to:

• Making existing facilities used by employees readily accessible to and usable by persons with disabilities.
• Job restructuring, modifying work schedules, reassignment to a vacant position;
• Acquiring or modifying equipment or devices, adjusting or modifying examinations, training materials, or policies, and providing qualified readers or interpreters.

An employer is required to make a reasonable accommodation to the known disability of a qualified applicant or employee if it would not impose an "undue hardship" on the operation of the employer's business. Undue hardship is defined as an action requiring significant difficulty or expense when considered in light of factors such as an employer's size, financial resources, and the nature and structure of its operation.

An employer is not required to lower quality or production standards to make an accommodation; nor is an employer obligated to provide personal use items such as glasses or hearing aids.

Title I of the ADA also covers:

• Medical Examinations and Inquiries
  Employers may not ask job applicants about the existence, nature, or severity of a disability. Applicants may be asked about their ability to perform specific job functions. A job offer may be conditioned on the results of a medical examination, but only if the examination is required for all entering employees in similar jobs. Medical examinations of employees must be job related and consistent with the employer's business needs.
• Drug and Alcohol Abuse
  Employees and applicants currently engaging in the illegal use of drugs are not covered by the ADA when an employer acts on the basis of such use. Tests for illegal drugs are not subject to the ADA's restrictions on medical examinations. Employers may hold illegal drug users and alcoholics to the same performance standards as other employees.

It is also unlawful to retaliate against an individual for opposing employment practices that discriminate based on disability or for filing a discrimination charge, testifying, or participating in any way in an investigation, proceeding, or litigation under the ADA.