Am I being harassed and discriminated do to my disability?

I work for an employee that requires yearly medical exams. When I was getting hired on, I passed all of the exams and still was sent to the company doctor to get evaluated for my disability (Cerebral Palsy). My personal doctor faxed them that I have no limitations and I am FIT FOR DUTY. I went to their doctor too, and he cleared me as well. Now a year later I pass all the medical exams again, but I received an email a week later that I have to go get evaluated by the Company doctor to sign off on my medical sheet. No body else that passes the medical exams goes and sees the Company doctor.
medical exam consists of eye and hearing test, eye pressure test, etc. we do have a physical test as well, which is done by the training staff. The physical test includes running and climbing stairs which were all passed twice within the year.