please help, save corrupted !

please help me, what should i do? my minecraft world suddenly reverted, what i had built and harvested disappeared, even my inventory reverted, for a short while i still had the conduit effect i had then it vanished , drove it with it and I lost all my builds, it looks like the game reverted to an old save game, and I can't do anything, I don't want to enable cheat codes; I beg you help me, I lost at least 50 hours of play I don't know how! Please !