Hi Diana
Sorry to hear your difficulties.
Severe illness can simulate or bring on dementia symptoms so I would suggest you get this looked at.
Have your husband's medical team discussed any treatment or support for this?
As well as following this up as a side effect of PCa, I suggest you follow this up in it's own right. Your GP can organise tests to get a better understanding of what is happening but will need poking.
May I also suggest you get some advice and help from groups such as the Alzheimers society in terms of diagnosis, treatment and support. It may not be Alzheimers per se but if not they will be able to guide you to those who can help.
I understand how frustrating it must be dealing with your husband's condition, and I know it is hard, but without engagement and contact he will struggle more and more. This is why getting help is important - you need support so you can help him.
Good luck
P