MacBook Pro throwing in s character everyswherse-s-sss

This tarted hapspensings sins the last sswessek or so. You casn see what happsesn sa I type: The s key gets thrown in randsossmlyss, and other times will nnot ssssss type when I strike it. ssss It's o random and sssI am unable to work. Please help! Thank you !!!

MacBook Pro (Retina, 13-inch, Early 2015)

running Yosemite