Almost 50% of storage is used by "Other" on MacBook Pro

I have a MacBook Pro 13-in, Early 2011 with a 2.3 GHz processor and a 320 GB SATA Disk Hard Drive. When I installed OS X El Capitan last year, I noticed significant performance loss, so much so to the point where I haven't been able to use the computer it is so slow. I just replaced the battery (which was beginning to swell) turned off File Vault, deleted almost everything including all iPhoto and iTunes delete folders, re-indexed my spotlight, and STILL have 154.41 GB of "Other" storage. I'm not sure what I can even do to get that storage back.

Any help would be great! I've tried almost everything listed on all of these forums and nothing has helped.