Mystery storage issue

Hi all Mac users,

My Macbook is really slow and many programs won't open. I thought that I may have used all my storage so I searched on finder on my computer under "get info" but this shows I actually have a plentiful 59.57gb available - as shown to the right. I investigated further and found on system report, under storage is reveals that I have 18.9MB available on the logical volume group. I'm now very confused and I can't understand what would be using apx 60gb of storage (half of my total storage capacity!). The top level structure totals the same as what is being used according to "My Computer" on the system report below so it must be something else using all this space. I am happy to provide any further details to help resolve this. In anticipation of your support, thank you.

My Computer:

Available: 60.57 GB (60,568,207,360 bytes)

Capacity: 120.1 GB (120,101,797,888 bytes)

Mount Point: /

File System: Journaled HFS+

Writable: Yes

Ignore Ownership: No

BSD Name: disk1

Volume UUID: 1FEFC322-35AB-347F-BC63-8B14F5045356

Logical Volume:

Revertible: Yes (no decryption required)

Encrypted: No

LV UUID: 2E42A19E-4D7A-41BF-99B7-DB35492F34C7

Logical Volume Group:

Name: My Computer

Size: 120.47 GB (120,473,067,520 bytes)

Free Space: 18.9 MB (18,948,096 bytes)

LVG UUID: 816ADFBD-740E-4AC8-B8DE-D429808BF1D0

Physical Volumes:

disk0s2:

Media Name: APPLE SSD SD0128F Media

Size: 120.47 GB (120,473,067,520 bytes)

Medium Type: SSD

Protocol: PCI

Internal: Yes

Partition Map Type: GPT (GUID Partition Table)

Status: Online

S.M.A.R.T. Status: Verified

PV UUID: 4078EF9C-4990-4B6E-AE5E-9B583C3586DC