I observed this sort of caring for an elderly parent at close quarters and it was a living nightmare for the family people who were carers. I truly don't know how they coped for all those years.
It was, sadly, a huge relief when she actually died.
Feeling you love someone and acting responsibly and caringly are two different things. You can choose to act caringly but no one and nothing in this world can make you genuinely love people who have acted in a way that kills your love for them.
And that's not bad. It's okay to not love them, though it might be wiser not to say so aloud. It's also okay to say 'so far and no further' because while yeah, I personally think you do have some obligation to aged parents, that does not mean you have to do everything for them.
When they expect you to do things that their carers can do, tell them that. "it's the carer's responsibility to do that, I have to go and do XXXX for my own family" "I'm sorry, I can't do that now, the carer can do it, it's her job". Repeat and if necessary, literally let yourself out of the door and come back when YOU can. Not when they demand.
They won't like it but think of your own family and maybe that will give you a bit of strength.
Your own family is the future, that's where your love and attention and care and concern mainly needs to go.
Love mostly goes -down- through the generations, not upwards; sure, some can go up but the most needs to go on to the next generatoin.
Can you talk to your partner at all? what does he think of this?