Hello,
@Honey15, and welcome to Talking Point. I'm sorry you have needed to find your way here, but hope you will get help and support and information. TP has been a lifesaver for me.
Yes, the deterioration is very difficult to watch, isn't it? I have a parent with dementia, not a partner, but we have many members here on TP who have, or are, caring for a spouse (and sometimes other family as well) with dementia. You're in good company.
Here is the thing: dementia, like Parkinson's, is a progressive disease. At some point, there is a downturn. It's a marathon, not a sprint. You have to conserve your strength, so you can keep going.
Another thing: dementia will take all the time and energy you throw at it, and be insatiable for more.
And a third thing: being a hands on caregiver, 24/7, is a really tough job, physically and emotionally. When you add dementia to the mix, it gets even harder. No one person can do it alone, 24/7, 365 days a year, forever, without suffering consequences. Dementia will break down your health if you allow it. Just the sleep deprivation alone (never mind practical things like lifting, personal care, the mountains of washing from incontinence, behavioural issues) can do you in, if you're not careful.
Never refuse help, and never be afraid to ask for help you need.
It's also smart to have an emergency plan, just in case, if you are the main carer. What if: you get the flu, or break your arm, or have to have an op, or need to leave town, or any number of things.
A good place to start is with getting PoA, if you haven't done already, and then with a needs assessment and a carers assessment. Others here on TP who know more about the UK system (if that is where you are) will be along to advise. Very best wishes to you.