You sound so like me!!!
I walked away from my career for mum and 4 years' later, I am still wondering how it will all end (and when I will get a good night's sleep again)
I spent this afternoon offering chocolate to a bunch of totally (to me) invisible people and trying to get my head around the fact that mum was constantly asking the adult me when the child me would be home from school. I am constantly mentally bracing myself for the accusations of being selfish, trying to abandon her and taking her money and then moved to tears by how kind and loving she is at other times.
The truth is that dementia is just a nasty disease! One of the best reads I had is the Stumped Town Dementia blog, which is still available, although the author's mum, the PWD, has now passed away. It's such an honest account of what dementia does to that mother-daughter dynamic.
I did something today that I found really helpful. I saw a job flagged up that I know I could do if I wasn't doing this and I used Mum's snooze time to practice pulling together an application. I read it back to myself in amazement, thinking, "Who is this woman? She's actually really employable!" I started working towards a professional qualification just before I had to drop everything and care for mum and I was already seeing myself as 'maybe too old' and going in via the 'experience' route. The youngest I can possibly be now when I finally reach my goal is 50, but so what? So what if I am up against people 10 or even 20 years younger than me? I have more to bring to the table and so do you. Taking care of a person with dementia takes guts! It takes levels of self-awareness, empathy and patience that I bet you had no idea you could achieve. Imagine taking those skills back into the workplace.
I am lucky in that mum did agree to a few care shifts, so I managed until 6 months ago to eke out a bit of consultancy work, but it became very hard in the end. However, it made me appreciate my profession so much more and unlike when I was on the hamster-wheel of full-time work, I have actually began to peek through professional journals and start to become genuinely enthusiastic and optimistic about my former profession again.
Please don't despair! You are not going to emerge from this as a has-been. You are going to emerge as an asset to any employer!