@deang68 Are you on Windows PC or Mac?
When you say saved to your Gallery, do you mean your Library? The Gallery is online whereas the Library stores Households/Lots/Rooms locally in the Tray folder in your Sims 4 folder. If you deleted everything Sims related from your computer, your uploads would still be accessible in the Gallery.
It sounds like maybe your computer is setup to store Documents files in the cloud when the internal storage is getting full. This means that the game can't find the contents of the Sims 4 folder to load, such as Saves and the Tray items, so it is like loading a new game every time you launch the game but if you could clarify PC/Mac that would help.