Q: How can i get data back from a backup that has lost all of my data?

Did you check in iTunes/Edit/Preferences/Devices if there are any other backups listed?

Did you also back up or sync your contacts  to iCloud?

If you have included the backup folder on your computer in your backup routine, you could restore the backup you need. Check these articles about it:

Create and delete iPhone, iPad, and iPod touch backups in iTunes

About backups in iCloud and iTunes - Apple Support

I use iCloud to back up my device automatically, and from time to time I back up to my computer as well, just to be sure...

Sorry, but if there are no other backups listed in iTunes, not even from another iPhone, in case you had one before, your data is gone.

Each backup replaces the old one, unless one is used to restore your phone from. This one will also have a time stamp and will not be overwritten.

If you did not enable iCloud backup in Settings/iCloud, or activated syncing contacts, there is no data to be restored from using iCloud as well.