Seeking forgiveness and strength in caring for a beloved sister

Assalamu alaikum. My sister requires constant care throughout the day and night for all her needs-from meals and washing to moving about and using her medical equipment. My father, may Allah preserve him, is her main caretaker, but his age is starting to show, and he finds it harder. I work two jobs to help with the expenses and assist at home with my sister as much as I can, but it can be incredibly draining. Sometimes, my mind is filled with worry about what the future holds for my father's and sister's health. Astaghfirullah, I love my sister dearly and would do anything for her. Yet, in moments of complete overwhelm, a terrible thought crosses my mind about how life might be less painful for her and less heavy for us if she... I can't even finish, as I feel deeply ashamed and disgusted with myself for letting such a thought enter my heart. I make constant dua for my family, but at times I feel helpless and fearful about what lies ahead. I am trying to place my complete trust in Allah, but I carry this heavy burden and often feel alone, as if no one truly understands. I sometimes ask, 'Why us? Why my father and sister?' I know every soul is tested, but it feels so intensely difficult and unfair, even as I strive to accept Allah's decree. I have personal dreams, like getting married and seeing more of the world, but I cannot imagine pursuing them and leaving my struggling family behind, for they mean everything to me. I pray for patience, ease, and strength for all of us.