I can't back up my realm Because all the back up somehow disappeared

I need this fixed right away if doesn't get fixed soon all my progress is completely gone For ever I went to go download  my relm to a world it was incorrect and when I went to go back it up  the back ups are gone please help months of progress will be gone I do have a back up but what I was building took a long time build and its gone now because the back up is an old one from a few months ago that I downloaded to a world