iPhone photo albums losing photos after syncing

Whenever I sync my iPhone 6, iTunes re-syncs photos that are already on my device, which always removes them from the photo albums I set up on my device. It's such a time consuming process for me to go to each My Computer folder in the Photos app and find the photos that were re-synced. Most of the time, it re-syncs the same photos as before, but lately it has been re-syncing other new photos and they get lost too.

So, the photos are never "lost", per se, but they keep getting removed from my handmade photo albums in the Photos app every time I sync my device via USB. I've tried other USB cords, and that isn't the problem.

I thought it was the iPod Photo Cache, so I deleted the folder and tried to sync my device, but then it wouldn't sync photos at all. Now, I restored the old cache, and the problem is back with it.

Is this an issue with iPhone 6? I updated to the latest version of iTunes on PC, and it didn't fix it.

If anyone has had this issue before, and found a fix, please reply to this!