Pregnant Snooki -- Why I Lied About My Pregnancy in 2012 ...

Snooki was LYING FOR TWO when she denied pregnancy rumors earlier this month ... but sources tell TMZ the "Jersey Shore" star had a damn good reason -- she didn't want to jinx herself.

Sources close to the MTV star tell us ... Snooks WAS already pregnant when she went on Sirius/XM radio on Feb. 1st and told everyone she was OUTRAGED by the suggestion that she had preggo belly.

But we're told Snooki is taking the situation very seriously ... especially the taboo about revealing the pregnancy before the 3rd month.

Now, it seems Snooki has crossed the 3-month threshold ... and an official announcement could come any moment.