My photos are taking up 5 GB on my phone and I only have about 100 of them. I do have a bunch of ghost photos that I can't delete though. They are from my old phone which is not an apple product and I am having storage issues because of it.
Assuming you have an iPhone; probably best to backup your phone through iTunes then do a factory reset and restore your data. If they are ghost/misbehaving photos then they won't be included in the backup and hence won't be restored back onto your phone.