Answer:
I'm a word that is not even strange. What am I?
I regularly change shape yet remain a sphere. I am always there but not often seen. What am I?
The last woman on Earth received a phone call. Who was the caller?
I belong to you but others use me more often than you do. What am I?
I am what bring things together. Without me everything you see would be a total mass or debris everywhere.
No matter how little or how much you use me, you change me every month.