There are too many copies of some images in my iPhoto Library on my iPhone

I keep getting a "updating iphoto library" with a progress bar, and every time it finishes there are certain photos that get two more copies added. I'm up to 14/photo. I'm pretty sure that the library isn't actually copying the photos or I'd be running out of space, but iPhoto shows 14 of the same image when I try to scroll through the library. Some images aren't being treated this way.