Some of my pictures transfer from my iPhone by iCLoud but some do not. Some of the pictures are taken the same day.
The problems you are facing can be solved if you understand the rules of iCloud's working methodology.
How to Understand & Work with Your iCloud Photo Stream
The below article lists some of the measures you need to take while using iCloud to syncing photos to it.
Photo Stream Not Working on iPhone: Fix Sync, Share and Other Issues [How to]
iCloud: Photo Stream troubleshooting
iCloud: Photo Stream FAQ