While you are at it, look for a washer with a small hole in it (flow restrictor), either where the hose connects to the shower head or where it connects to the faucet assembly. If you are not concerned about water usage or figure you can learn to regulate it yourself, remove the washer (flow restrictor) and you will get a much better shower.
Some people change to a different shower head trying to fix this, while the removal of the restrictor is all that is necessary. Try it and if you don't like the results, put it back!
You will find one of these in every faucet (kitchen, bathroom, outside shower). It is a way of saying you're an idiot and can't regulate your own water use (IMHO). I removed all of ours and we enjoy better flow at every faucet. The family has learned how to conserve water (when "dry camping") even with the restrictors removed.
Try it out!