So I have this problem with the camera roll of my iPhone SE

It doesn’t let me take any photos/videos, it doesn’t save any screenshots or screen records, and when I try and delete photos/videos they just come back seconds later; it also doesn’t let me post anything on Instagram, if I press the icon to post a photo/video it comes up blank - I’ll be lucky if it works on snapchat. It’s been happening since the 4th February 2018, and my storage is not full whatsoever (and I’ve made sure of that, multiple times). Can someone please help because it’s making my life very difficult and it’s extremely irritating because I don’t want to have to be restricted