Perhaps you moved or deleted your catalog file when you were trying to free up space. You need to find your catalog file and then double-click on it to open it.
I don't believe I did move or delete my catalogue. Where can I look for my catalog file. Why does my Lightroon now contain more images and ones I don't want on it, without my physically importing them?
Pablo, what is your OS?? But search your computer for files ending in .lrcat - they are the catalog files.
Let us know what you find..