I don't know what you mean by "iCloud reset itself" - if you are refering to photo stream, then if you deleted your photos from that and disconnected from photo stream and reconnected, then your photos are gone. If you had them in your camera roll and you made backups to icloud, then the photos may be salvaged by performing a restore. Here's some info on lost photos..
Many users have lost photos while preforming a restore from backup or upgrading the iOS. Recall, only photos in the camera roll are backed up to iCloud. There is a way to turn backups for camera roll on/off, perhaps these users had camera roll turned off.
Settings>icloud>Storage & Backups>Manage Storage, tap the device's name and on the next screen, be sure Camera Roll is turned on.
Photos should be regularly synced to a computer (like you store photos from a digital camera) using either USB via iTunes (on a mac use iPhoto or Aperture to move them to an album) or using photo stream. If using Photo stream, but sure to move the received photos to a permanent album. If you have been doing that, then you can sync those photos back to your device.
Or, you can fiind other apps in the app store that send camera roll photos to a service like Dropbox.
If you haven't been saving photos except relying on iCloud to store them in a backup, then that is risky, as many users have discovered. I'm afraid I have no advice in this case - there is no "cure".
IF YOU DID PERFORM BACKUPS TO ICLOUD, here's info on performing a restore...
Go to Settings>General>Reset and tap Erase All Content and Settings. This will erase your device. Then you will go through the setup screens again as you did when your device was new, and when given the option, select Restore from iCloud Backup.
This link gives another overview of backup and restore: