You could reset your phone settings, About, Reset phone. As something went wrong when applying your data backup. Try resetting, log into your outlook account when your phone asks, it will look for a backup and apply the backup.
**Note some settings and ir messages may not be applied as they may differ from those in Windows Phone 8.1**
Try the reset and if the problem persists you won't be able to apply your backup. Only option is to downgrade back to 8.1 if your messages and such are hugely important.
There a new app you might want to use in the future from Microsoft called contacts and messages.It backs them up to sd card.I used it when upgrading from 630 to 640 Las week.Worked a treat.Once installed.This feature appends on to your settings at the bottom