Sudden Storage Fluctuations/Free Up

I’m experiencing something strange with my phone’s storage, and I’m not sure what’s going on. Last year, I had nearly maxed out my storage at 255/256 GB, but suddenly, it dropped to around 100 GB, and now it’s fluctuating again—it decreased to 99 GB today. This is concerning, and I’m wondering if something might be wrong with my phone. Could someone help me understand what’s happening?

Here’s some context: my phone was being used for filming a school project, and I often got “insufficient storage” notifications. To make room, I deleted some apps, but I was still hovering around 250-253/256 GB of used storage.

Later, I heard that getting iCloud storage would free up space by storing photos in the cloud, so I subscribed to 200 GB of iCloud storage. I used it for about a day but then canceled the subscription after hearing it wasn’t effective at freeing up much space. Unfortunately, I didn’t check my storage before canceling the subscription, which I now realize was a mistake.

In December, I took a lot of photos and videos during trips, but I didn’t check my storage, assuming I’d hit full capacity soon. However, just two days ago, I checked my storage and was shocked to see that it had suddenly dropped to around 105 GB. This morning, it dropped again to about 100.96 GB. I read in an article that this could be a bug and that updating the software might help, so I updated my phone to iOS 18.

After the update, I checked my storage again, and it had dropped further to 94.16 GB. Then, in the same minute, it fluctuated to 94.99 GB, and four minutes later, it went down to 94.65 GB. Now, as I’m writing this, it’s back up to 95.58 GB.

Could anyone explain what’s going on?