Hello
@Seabream and welcome to the Dementia Support Forum. Twelve years is a long time to be caring for someone and now that there may be dementia in the mix it is obviously more difficult for both you and your husband. It is not clear from your post if your husband has been formally diagnosed with dementia and if not i would suggest that you contact his GP to discuss your fears.
@SherwoodSue has also given you good advice to discuss your own health with your GP, you are also important.
Do you have any help caring for your husband, if not, please contact your local adult social services to arrange a needs assessment for your husband and a carers assessment for yourself.
Please keep posting on the forum, to ask for advice or just to let off steam, our members really do want to help and are very knowledgeable about all aspects of dementia. You might find it useful to start a thread on the - I care for a partner with dementia - forum, I have attached a link