Photoshop PSD converts all my layers into one background layer! HELP - Duplicate

I have all the layers perfectly in front of me and I go to save as and click to save it as a PSD and make sure to check the [] Layers. After I save the file, I get a maximum capacity notification.

Then I go to open the document and it is a single background' layer, which I'd removed, is back, completely flattened picture of all my layers merged into one called the background layer.

I still have another file that is in my recents, but whenever I got to open it and save it to send to my teacher, it all of the sudden goes back to one locked background layer of my flattened picture. HELP.