How can I get rid of a memory glitch cause by iCloud?

I have the iPhone 6 and for the longest time I've had a memory glitch. I took it to the apple store where they told me that it wasn't the phone itself, but the iCloud. They gave me a new phone and told me in order to get rid of the glitch I can't back up anything onto my iCloud and reset my phone. So I did so, but then two weeks later after everything was going well, a significant drop of storage happened. I went from having 9GB to 3GB in a matter of seconds. All my apps usage didn't add up and every time I plug it into the computer it says the correct storage that it should be. I created a new iCloud account and shared files with my old accout so none of my photos would be lost, but the same thing occure two weeks after. The only way that I can get rid of it is resetting my phone and loosing everything, but it only lasts about two weeks and I'm tired of having no storage available and making new accounts for the same thing to happen. What should I do? I've had this problem for about a year and a half now and it continues to happen no matter how many iCloud accounts I make.