Water pressure? This past week I suddenly lost river pressure in my shower....

This past week I suddenly lost river pressure in my shower. It very soon puts out roughly half the wet pressure it had earlier
any Ideas how to fix?

Beyond stating the obvious, I am trying to put aside money so buying a new shower chief, while a good answer, is not what I would close to to try first
How to build a deck takings or plans...
Answers:    clean it within vinegar over night.have the rest of the house lost pressure...bigger problem...muni supply or pressure regulator.
How do I choose best answer?
If water pressure isn't adjectives that great in your home..you will hold to choose between pressure & volume..If you want lots of water..you won't own much pressure..Most shower heads in this day and age are designed to use very moderate rates of sea..If your showere did work good & immediately it won't..perhaps it is newly in the faucet..or the herald needs to be cleaned.