Answer:
I go from house to house a messenger small and tight. Whether it rains or snows I sleep outside at night.
I know a word of letters three. Add two and fewer there will be. What is the word?
What body part is pronounced as one letter, but written with three, only two different letters are used?
What force and strength cannot get through, I with my unique teeth can do. What am I?
I twist and turn and leaves a loop
No matter how little or how much you use me, you change me every month.