Q: my iPhone 5s won't back up to iCloud and it's not saying storage is full.help please ??

This is Apple's support document for help with iCloud backups.

Get help backing up your device in iCloud - Apple Support

IMHO, It is basically useless and covers the most basic things that anyonone should already know. Makes sure that you are connected to WiFi....Duh? Yep, thanks for that one.   In any event, I just wanted to share my experiences backing up to iCloud. It can be very hit and miss for me. Just two days ago, I struggled to manually backup my iPad and iPhone and just kept trying and trying. I kept getting the message that the backup could not complete. That's really helpful. Thanks Apple. I knew that when the backup wouldn't complete.

Anyway, the best advice that I can give is to keep trying. You can try toggling WiFi off and on, Sign out of iCloud and sign back in, restart your phone, turn off Find my iPhone, wave a dead chicken over your head and burn incense. The one and only thing that works for me is to not give up and just keep trying.

BTW, I find that iTunes is a much more reliable means of backing up, but once again, that's just my own worthless, humble opinion.

I suppose that what I am trying to emphasize is that there is no rhyme or reason to how these confounded iCloud backups work. You just have to stay at it and try different things to get it to work. Some users have no problems at all, and I never had problems with iCloud backups until iOS 9 came out last fall. That is when I started having problems.

I Hope that you get it resolved!