How do i fix my shower?

My shower spout all of a sudden has lost its water presser. Like if you turn it on all the way it just kinda drips/really low stream? Our water is turned on and everywhere else in the house water works fine. Do i need to buy a new shower head? I know the one i have is pretty old. Any ideas what i can do? Also if i do need to change the shower head is it pretty easy to do?