Messages in iCloud Storage

I recently noticed when I went to check my iCloud storage that most of my filled storage is from Messages, taking up 4.4 GB of storage. When I checked to see what kinds of images could be taking up so much storage, I was shocked to see that the Top Conversations were only 36.1 MB. I am pretty sure I heard somewhere that each device with access to my iMessage, like my MacBook, iPad, and Apple Watch, individually takes up iCloud storage. So, because the Top Conversations were 36.1 MB, I'd expect that my MacBook, iPad, and Apple Watch all used 36.1 MB in my iCloud storage (36.1 MB * 4 devices = 144.4 MB across 4 devices). However, 144.4 MB is nowhere near the 4.4 GB Apple says Messages is taking up my iCloud storage.

My only conclusion is that the 144.4 MB is purely text and the rest of the 4+ GB is images, but whenever I open Messages on my iPad, none of the images people have sent me have loaded, and I have to manually load them if I wish to see them (my MacBook loads the images). I know I could probably import my notes from Apple Notes to another note-taking app for some extra storage, but that just leaves more room for Messages to take up. How do I fix this issue? I need some more iCloud storage, and I am not planning to buy another subscription again.