Have you created multiple backups of the same files causing them to appear as duplicates? What are you currently using to back your device up?
If you have multiple locations on your device for the same photo or video, it could produce multiple images.
I would recommend checking your Backed up files and storage to ensure for every "picture" you take that two copies aren't being saved, One as the original and the second as the backup's copy.
Hope this finds you well
Let us know if this resolves your concerns