She said of her dad: "He was having sex with girls under the boardwalk in New Jersey before he went to see Bruce Springsteen.
"He saw a lot of himself in me. My first piano teacher was a stripper. My dad told me later. I used to say to her, `Why do you have such long nails?` She just said, `Someday you`ll understand why`."
The singer - wearing a latex two-piece outfit - spoke candidly to American radio presenter Howard Stern.
Famed for her outrageous dress sense, she told him: "I don`t like pants. I affirmatively agree that women should not wear pants. They`re a health hazard."
The saucy star also bragged that she had had SEX just hours before the interview.
She told Stern: "I got laid last night..."
GaGa, crowned America`s most powerful artist earlier this year, quit college after a year and claims she was "an a******e at school" who had affairs with other women.
The New York-born Poker Face singer said: "At school I didn`t know who the hell I was."
However, she insisted she had a strict upbringing as a youngster - revealing that it was her dad who forced her to quit Class A drugs.
GaGa said: "I was for sure addicted to coke. I got off it because my father called me out and kicked my a***.
"I didn`t do it with people, I did it alone. But I regret every line I did."
The star confessed she still smokes marijuana, insisting she wanted to be honest with her fans.
"I don`t do weed that often - and I tell the truth about that," she said.
"I don`t respect artists who aren`t honest about what they do recreationally."
The saddest time in GaGa`s life was six months ago when she lost her grandad, also named Joseph.
She said: "My grandpa was dying and I was heartbroken.
"The only two times he moved was to squeeze mine and my grandma`s hands."
She wrote her song The Edge Of Glory when she arrived home from visiting him in hospital.
GaGa said: "My dad and I sat at the piano doing shots of tequila and I said to him, `Grandpa`s about to pass into his moment of glory. He`s on the edge`.
"He just said, `That`s it kid`. I recorded it that day and I took it in and played it to my grandad. I know he heard it."