gas gage problem

My gas gage on my 95 cavalier is completly messed up. the needle points to whatever it wants to sometimes it says its full then 5 min later will say empty then go up to a quarter tank of gas and so on. when i take a turn it doesnt effect this i could be sitting still at a stop light and it will still move. some one please help me im tired of running out of gas in the middle of no where

Sending unit? It seems it's not reading correctly......my truck does this and still does.....the needle on mine vibrates and moves.......also a Chev, my cavalier hasn't done it though.