Storage Leakage Issue

Hi guys, just wanted some help with a major issue I've been having.

For the last couple months, my Macbook Pro (High Sierra 13-inch, Early 2011, 2.3 GHz Intel Core i5 and 480gb) has been steadily losing storage space, sometimes as much as a full gigabyte a day, for no reason. There is little to no increase in my files and I've actively deleted at least 80gb of storage from my user to literally no effect - it only decreased my storage.

No matter what I've done, nothing has helped. Furthermore, I've deleted around 90gb of old "Other Users" data, so much so that for the "Other Users" should only take up 45gb of storage (one takes up 35gb, the other 10gb according to the "Get Info" screen). However, it apparently takes up 229gb of storage, even though it literally does not.

This whole issue is extremely frustrating, as at this point I've deleted around 170gb of data, some of which had some sentimental value, so any help will be massively appreciated. And before anyone asks, yes I've emptied my trash.

P.S. Whilst I was writing this, I lost 0.04gb of storage.