ok .... I'll propose a different angle. You said you are not responding favorably to carbidopa/levadopa also known as Sinemet. First and foremost, (as stated) everyone with parkinson's has unique symptoms and responses to meds. Having said that ... Sinemet is usually the 'gold standard' ... works the best. It's sometimes used as a diagnostic tool ... if respond favorably to Sinemet in combination with some other symptoms, bingo .... dx is pd.
I may be assuming too much, but it sounds like you have never responded favorably to Sinemet. Is that correct? If so ... are you comfortable with a diagnosis of parkinson's? Do you see a movement disorder specialist (mds)? Makes me very curious/doubtful/inquisitive about the diagnosis.