macbook showing wrong storage space

I bought a 256 GB Macbook Pro a few months ago and recently it has been displaying an incorrect amount of storage. It says I have 165.71 GB of apps taking up my harddrive, and this number keeps increasing rapidly every so often. However, there is hardly anything on this computer. When I check the amount of space the apps are actually taking up it says it is about 18 GB. Does anyone know a fix to this?