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Multiple sources close to The Situation tell TMZ … the MTV star‘s hard-partying ways were worse than ever during the taping of the most recent season of “Jersey Shore” … and the signs were obvious during the episode when the gang went camping.

TMZ broke the story … Sitch recently checked into rehab for substance abuse after realizing his recreational habits had spun out of control.

Now, sources close to Sitch tell us … the reality star had been showing signs of substance abuse for a while … but “he was getting worse” as the season went on.

We’re told … several people noticed he was “acting paranoid” on the set … and the unusual behavior was evident in certain Season 5 episodes that recently aired on MTV. During the ep when the gang goes camping, Sitch can be seen acting jittery, sweating profusely and just plain acting bizarre.

Sources say … cast and crew members on “Jersey Shore” are happy he’s getting help … and hope that he will be healthy enough to join them for the recently announced Season 6.