HE’S the famous bad boy rapper whose lyrics are full of boasts about his sexual conquests. But in reality Eminem is a flop in bed, according to his ex-mistress.

“I was surprised,” says Kesia Alvarez. “He raps about having this bitch and screwing that one but he didn’t know how to excite a woman.

“I taught him a lot – an awful lot. He was like a little virgin boy when I met him… and he was 26 at the time. A lot of the stuff he raps about is bull****.”

The 30-year-old Brazilian beauty, who dated the star for 16 months, claims their disappointing sex life was, in part, due to the singer’s small manhood.

“He has a very tiny thing, nothing to tell your girlfriends about, and when we were together he sometimes suffered from premature ejaculation.

“The first night, it was all over in 20 seconds. He wasn’t even a one-minute man that time. Sometimes I had to work real hard to get him to perform. He was mortified about it.”

During a European tour, it became obvious that Eminem’s size problem was well known among his entourage.

“In Germany, there is a snack called Dickmans,” explains Kesia. “We stopped to get some munchies and his bodyguard came out with packets of Mini-Dickmans. He handed them around to us all and everybody was laughing.” Kesia was by Eminem’s side during tours of the US, Britain and Europe and even stuck by him as he wooed and wed wife Kim in 1999, in a marriage that lasted less than a year.

Kesia, a manicurist from Florida, met the 31-year-old singer when he was signing autographs on Miami Beach in March 1999.

“I didn’t really know his music and I certainly didn’t like it at the time,” she says. “But, for a laugh, I grabbed a pencil and paper and asked him for his autograph.

“As we faced each other, it was like, ‘Wow!’ We both felt it. We were staring at each other. Then he asked if I wanted to go to his show that night. He was very sweet and flirty. He has a very charming manner about him.

“After the show, we hung out together and got on really well.”

Most of the singer’s friends called him by his real name, Marshall Mathers, although some nicknamed him Slim after his violent record alter-ego, Slim Shady.

“That night, we ended up passing out together – simply because we were so tired talking,” Kesia continues. “Next day, Marshall said he was going to north Florida for a break and would I go on his tour bus with him?

“I said no, because that’s a groupie thing but I said I’d drive up.

“I stayed there three days but I still didn’t sleep with him.

“I’d no sooner left than he began phoning: ‘I miss you. I really like you, I have to be in California next week, would you like to join me?’ I said yes.”

As soon as she arrived, Kesia says she met rapper Dr Dre – and Eminem introduced her as his wife.

That night they slept together for the first time. “He was nervous. I was the one who had to take control. It was so disappointing.

“As soon as we started, it was over. I didn’t even know what happened. All he did was apologise again and again. He was a good kisser, though.”

During their relationship, Kesia used to cut and bleach her lover’s hair and select his clothes.

“Marshall would call me his Brazilian princess. My pet name for him was ‘My baby brat husband’.

“I didn’t mind being Marshall’s mistress. I was in love with him and he was in love with me. Despite not being a great lover, he was the funniest man I’ve ever been with. We had a great time.”

But as she spent more time with him, Kesia realised how confused he really was. “He was really blown away by all the money that came in. It was stressful for him.”

By May 1999, Kesia says they’d fallen head over heels in love. Yet despite their romance, he still married Kim, the mother of his seven-year-old daughter, Hailie, the following month. Kesia says: “Marshall is a wonderful father and adores Hailie. He told me that she was the only reason he was marrying Kim rather than me.”

Kesia’s story is backed up by Eminem’s former bodyguard, Byron “Big Nasty” Williams. After splitting from the rapper, he penned a book about life with the star called Shady Bizzness.

In it, he wrote about Kesia: “She was cool and we regarded her as more than just a groupie – and she was definitely more mentally stable than Kim.”

Both Kesia and Williams remember how, in May 1999, the rapper pleaded with her to join him on tour in Michigan. But as Kesia flew up, Kim also decided to visit.

Kesia laughs: “They had to smuggle me out while she was checking in. Kim knew nothing about me but she found out because I left a message on his hotel room voicemail saying I loved him and I was sorry I’d had to leave early.

“Kim picked up my message and Byron told me later that the entourage came up with the story that I was a crazy stalker who called every hotel leaving messages.

“Kim didn’t really buy it but she and Marshall kissed and made up nevertheless.”

That June, Marshall married Kim, though Kesia says her love rival regularly treated the star badly. “She would often kick him out of his own house in Detroit and he’d have to stay at a hotel. He always referred to her as a bitch – he thought she was a vindictive, abusive drug addict,” she claims.

But it wasn’t long before Kesia and Eminem started having their own problems.

“He’s a very volatile, angry person. As our relationship developed he got physical. It was rough-house stuff – sometimes as a part of sex – not real beatings.”

She claims the rows were fuelled, in part, by Eminem’s drug-taking – although the only drug he has ever admitted to taking is the prescription painkiller Vicodin.

“He was a big user of Ecstasy and cocaine, as well as prescription downers, Zanax and Valium,” claims Kesia.

“I don’t think he ever gave a show when he wasn’t high. He also drinks a lot of Bacardi and while I was with him he started on cognac, which he learned from Dr Dre.

“But he never smoked cigarettes and I only once ever saw him smoking marijuana.”

Kesia claims the rapper became more emotional as his alleged drug use escalated. “He did a lot of Ecstasy and he and some of his friends were heavily into coke as well. Many a night I had him with his face buried in my lap, crying, telling me how his family was screwed up.”

Kesia also alleges: “One night he asked me if I wanted to do some cocaine with him and I flipped out because that’s something I’m completely against.

“About a week later, I went into his hotel room. There was a plate piled with cocaine on the table. It was in a big heap, maybe a quarter of a pound. I flipped and hit the plate across the room. Suddenly, it was snowing…”

Eminem’s sexual performance – never great according to Kesia – also seemed to suffer because of his alleged drug use.

Kesia also wondered about Eminem’s sexuality, although she never saw any evidence of him being gay.

“He’s very homophobic but I think he protests too much.

I NOTICED on tour that he was often surrounded by young men who seemed gay to me – particularly when we were in Europe – and he would mysteriously disappear sometimes.”

When they were apart, Eminem regularly phoned Kesia, saying he missed her, loved her and couldn’t write new songs without her by his side.

But Kesia believes the singer’s manager, Paul Rosenberg, and road manager, Marc Labelle, may have turned him against her because she distracted the star from his work.

Their romance began to fall apart in 2000 when Byron’s book came out containing several references to Kesia that sent Kim into a rage.

“By this time, I’d had enough,” says Kesia. “Marshall was a big star and it had changed him. He’d become rude and arrogant. Slim Shady had taken over.

“At one point, in July 2000, I was afraid I was pregnant. I tried to discuss my worries with Marshall but he was having still more problems with Kim and refused to talk about it.

“We had a row and that was the last time I saw him. Luckily, my ‘pregnancy’ was a false alarm.”