I agree with Mimi, we need to know more about the person for whom you're caring. Are you a spouse, a child or other family member or friend? I'm assuming you're a spouse, but if not we should know your relationship with the person with dementia.
When was the person with dementia diagnosed and did the physician rule out all other causes for the condition? What issues are you dealing with and when you say "3rd stage dementia" are you referring to the stages on the Fisher scale? would also be helpful to know the person with dementia age and yours too. We all want to help but we need a bit more info.