WHEN she turned 21, “Survivor” competitor Dana Lambert shocked her mom with an oddball birthday request – a stay in rehab!

The self-proclaimed “butchy” blonde says she was hooked on speed, but now she’s convinced her struggle with drugs will help her win the 25th season of the hit CBS reality show.

“I guess being in a small town, I was bored a lot of the time so I turned to drugs,” said Dana, who grew up in Blytheville, Ark.

“I was 20 and addicted to amphetamines. I woke up one morning and said, ‘This is not the life I want anymore.’ ”

After deciding to seek help, Dana said her stunned mother asked: “You’ve got a problem with drugs?”

Dana spent 28 days, including her 21st birthday, in rehab, and she’s been sober ever since.

“I definitely learned from that and I do think it will help me in the game. I do well under stress,” said Dana, now 32 and an “out and proud” lesbian who works as a hairstylist in Winston-Salem, N.C.

A “Survivor” insider added: “Dana comes off as this innocent country girl, but she came out of the closet in her teens while living in ultra-conservative Arkansas and beat drugs in her early 20s. As a result, she’s a truly resourceful ‘Survivor’ player.”

Dana has also impressed show host Jeff Probst, who said: “I love the fact that she’s overcome so much, yet she’s made something of herself.”

But Dana admits she’s had to overcome one big fear while competing.

“I thought my biggest fear would be swimming in the ocean because I’m afraid of sharks,” she said. “But, truthfully, what I was scared of the most was talking in front of the camera. I was terrified of it !”