First, people's living conditions in modern society are better, and the elderly can generally live to 80 or 90 years old, so don't worry.
Although I don't know your age, there is one thing you can do well, and that is filial piety. You can be filial to them no matter how old you are. As long as your parents are still alive, you should make them happy That would be great.
Third, you may not be 18 years old, and it is right for your parents to take care of you. In the future, whether you are working or studying, you should repay them well.
As for your worry about birth, aging, illness and death, it is a natural law. Your parents will support each other and grow old together. When you grow up, they are really old, and you still have your lover and children. They will accompany you to your old age.