Showerheads tend to become clogged after years of use, usually from mineral deposits, and that can impact water pressure. The good news is, there is an easy solution with a household staple.
If the showerhead can be detached, soak it overnight in a bowl of white vinegar. If not, fill a ziplock bag with vinegar and place it over the showerhead, securing it with a rubber band. Leave for 12 hours, then remove the bag and run water through until the water clears.