An extensive workup should be considered for a 40 year old with progressive cognitive decline including an MRI of the brain first and foremost (especially because your doc says that there's been ?"shrinkage". Spinal tap should also be considered. There are a number of neurodegenerative diseases that present with early onset dementia and personality change such as Pick's disease as well as other diseases that are accompanied by movement disorders. Another important test would be a neuropsychiatric exam to show exactly what you're missing and where you're at right now in terms of cognition. Consider a major academic center for further evaluation. Best of luck.