Duplicate photos, never Synced Photos with iTunes

iPhone 6 plus, iOS

Pls help with my issue.. at some point (no, iPhone was not plugged to computer, just at some random time) my Camera Roll suddenly shows 2 photos of everything.. recent photos taken after that point does not show duplicates, just the photos/pictures taken until then. So this rules out the HDR.

Then I read through apple discussions, most of the cases ppl point that you may have synced photos through iTunes, well this is not the case..

When this happened, i was downloading some Games app updates, when notification box popped out saying i have little storage left in my device. So I went to camera roll and deleted a bunch of photos and videos.. This happened a couple of times, and at one point BOOM all my photos have duplicated ??!?!?!!?!!!

Just plugged in to my iTunes to double check that Sync Photos box isnt ticked.

HELP!!