I dreamed that my father was ill.

First, it reflects that you are worried about your father's health, and you naturally feel sad because you can't distinguish between true and false dreams.

Second, in reality, you may feel that your father is dissatisfied with something, and you will feel guilty and uneasy about it, so your dream father is terminally ill, which reflects a kind of self-punishment.

Third, the emotions in dreams sometimes accumulate depression in reality.

You are so sad in your dreams that you may encounter unhappy things in your life. Father represents a sense of faith and security.

Father's illness in the dream shows that this belief has been hurt and shaken.

It should be one of the above three possibilities.