LINDSAY LOHAN RIPS HER OWN MOVIE It Sucked!

Lindsay Lohan knows ... her stripper movie "I Know Who Killed Me" was so bad, no one should ever watch it ... EVER ... at least that's what she's telling her fans.

Lohan -- who's still in rehab at Cliffside Malibu -- was allowed to play around on the Internet yesterday (which happened to be her birthday) ... and responded to a fan who had tweeted her the following message:

"@lindsaylohan can you tweet me I seriously watched I know who killed me twice last night."

Lohan's response was classic -- "two times too many!"

For the record -- it's not THAT terrible ... as long as you watch it on mute.