OK. Sorry for all the questions Eileen
Can you tell me anything more about the white lesions on the scan--did the neurologist comment on them at all?
I don't think this is chemical poisoning Eileen.
The white lesions and your symptoms I think indicate a problem with multiple sclerosis and if so that can be treated with different medications than the ones you're on now.
You need to speak to the neurologist about getting another MRI of your brain and having a spinal tap to investigate that possibility