I think this question has been asked here before but I got to isolate the problem. I've been having problems with my macbook pro from a few days now. Suddenly I had no space left in my hard drive, and I wasnt downloading anything or deleting anything. Sometimes the storage also increased, but it mostly went down until I couldnt literally use it and had to restart. Talked to apple support, they told me to restart the SMC and NVRAM, didnt work. Then they said reinstalling the OS might work. Already did that and I see how my hard drive storage is decreasing (at a much slower rate this time though). I used omnidisk sweeper and it seems that it is the OS that is changing sizes, suddenly it is 12.88 gb, 10 mins later it is 12.95.
My computer is a macbook pro from 2015 and I'm using macOS High Sierra 10.13.6
What could be going on?