I've been to the hospital more times than I can count—if I had to guess, I would say probably 100 times through the years. By the time I was diagnosed, I was stage 4. It was everywhere.

Danica McKellar is aiming to educate and entertain young readers in a new kids book. PEOPLE can exclusively share the cover of I Love You 100: A Counting Book Full of Love, the latest book from ...