First off make sure it is the turntable. Do your other sources sound normal to you?
If they do you have a problem either with your cartridge or phono stage. Look at the cartridge carefully, it the cantilever straight? It the diamond still there at the end? Does it look normal under magnification? If you have another cartridge set it up and listen. If it sounds fine the first cartridge is defective. If it sounds bad you have a problem with your phono stage.
Good Luck