Why has my shower head stopped spraying?

Most shower heads are easy to unscrew. If you can do so, take it off, examine the head and see how much flow you have with no head in place. Don't unscrew the supply tube inside the wall! Unscrew the shower head from the supply tube.

When you screw it back on, usually you don't need pipe dope or Teflon tape on the threads because the usual head has a rubber seal that the end of the supply tube presses on. Over time the seal may be hardened and lose the ability to seal.

Does this head have a knob to change the spray pattern?

Schmutz in showerhead holes.

This happened to me. Schmutz had come down the pipe (it was blue!) and occluded holes in the shower head. They rinsed out ok. We had to do that periodically until whatever was giving rise to these blue particles was used up.

If you have particulate matter from old pipes or hard water it could do the same thing.

Soak in CLR , Wink or Iron out. These are the brand names of cleaners to clear, shower heads and sink screens. Works great if you have hard water or rust stains in tub. Has many uses.Should be done monthly.