Hi,
sorry to hear of the problems you are going through, have only a couple of things to add to what Laura has told you. the first is that not all parkinsonism is going to be parkinson's plus so please at this stage do not stress about that, there are a whole lot of other related conditions and they do not all spell the worst.

the other thing that you might consider if you are doing a sinemet challenge and getting no response from the medication is that the levodopa is not actually getting to the brain because of poor absorbtion - it is a possibility, especially as you are having some problems with nausea, and could also be caused by protein intake, you could try restricting protein till late in the day to see whether there is any effect from the medication.

hope that your issues resolve, it does sound like pd, but it is notoriously hard to diagnosed as some of us here have found! best wishes in finding a treament that suits you and a diagnosis too.

lindy