Which device contains your songs? The iPad or the iPhone? If the iPad contains your songs but you only enabled iCloud sync on the iPhone, you are one step away from losing all your songs!!!
iCloud sync needs to be enabled on the device containing your songs first! Then on the other devices.
You need to resolve the situation following these steps:
- Create a full backup file on your iPad via Settings > Create Full Backup.
- Disable Cloud Sync on your phone
- Tap on Delete Cloud Data on your phone
- Enable cloud sync on your iPad. Restart the app and wait for the sync to finish
- Enable cloud sync on your phone.