Welcome to the forum pgtips
I'm really sorry to hear that you are out of work because of Parkinson's and I understand why you might feel shortchanged.
Adjusting your meds regime is a constant balancing act. When they are working well I find that I have few visible signs of Parkinson's, if any. I'm 48 and was dx nearly 10 years ago.
There are a good number of working PwP on the forum and there are lots of posts discussing the pros and cons of working with Parkinson's on the forum. One of the advisers on the wonderful Parkinson's UK helpline specialises in employment issues. It would be worth giving him a call.
As Semele says there are laws (primarily the Equality act, except in Northern Ireland) that make it illegal to discriminate against you because of a long term health condition. In general you are not compelled to tell a prospective employer that you have Parkinson's and they are not allowed to ask.
I hope that helps