What's wrong with my icloud?

I have a iPhone 5s and it kept popping up that I was almost out of data in it. I have 5gb storage but it says I need an additional 2.4 to back up. I managed my settings to what goes on there and I only have my photos on it and it is only 2.6 gb and besides that I have nothing on it. Where is the additional gb coming from. I've deleted my backup and signed out of my account I don't know what else to do.

Make sure to turn off your photos and apps sync off otherwise it will sync and will fill the whole 5 GB storage if its already sync log in at web to icloud.com and remove your photos.