In order to be subject to the FMLA, a company must have 50 employees within a 75 mile radius of your workplace. In order to be eligible under the FMLA, you must have worked for the company for one year on a full-time basis (1,250 hours).
Even if the FMLA does not apply to you, it is still possible that you could be entitled to accommodations under the disability discrimination statutes. You should discuss this with a local employment lawyer.
An employer must have at least 50 employees to be covered under the FMLA. However, courts also recognize a theory of "joint employment" under the FMLA where more there is common ownership or control of a number of small entities which, when added together, have an aggregate of at least 50 employees. As an employee, you must also have been employed by the company for at least 12 months and worked 1250 hours or more during that time period to be a covered employee under the FMLA. You also mention, however, that you may have a disability. The Americans with Disabilites Act ("ADA") applies to any employer with 15 or more full or part-time employees. Under the ADA, there is no requirement that you be there for at least one year or that you work a certain number of hours. Intermittent time off for medical treatment may be considered a reasonable accommodation under the ADA even if the FMLA does not apply to you.