Answer:
my rings are not worth much but they do tell my age.
I know a word of letters three. Add two and fewer there will be. What is the word?
I will go within you and destroy you. Only because you wanted me too
While you were folding a letter you got me. Usually you will do whatever it takes to avoid me but now you can't help but find me.
I reach for the sky, but clutch to the ground. Sometimes I leave, but I am always around. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.