It’s a cliché — seen in shows from “Sex and the City” to “Girls” — that dating for women in New York City is rough. That men cheat and are immature. That finding the right guy is nearly impossible.

But according to sex therapist Dr. Brandy Engler, it’s much, much worse.

Take Charles. A successful engineer, Charles was jilted by his fiancée on his wedding day. Years later, he forces his new girlfriend to play-act that she’s two-timing him.

It’s the only way he can get sexually excited.

“Tell me how you’re going to do it!” he commands.

“In the bathroom — while you’re in the next room,” she responds half-heartedly.

This wasn’t a rarity, Engler says. She even remembered from her psychology studies that a former call girl testified that her most common request was “to sexually re-enact old traumas.”

Of course, Charles’ relationship became so weird that the girlfriend started cheating on him for real.

It’s just one of the many tales of dysfunctional sex that Engler encountered at her Times Square office — confirming her belief that New York men are a breed all of their own.

“There were times I felt repugnance,” Engler admitted. “Sometimes I had to work hard to hide my instinctual reactions.”

When Engler opened her practice in 2005, she expected to treat women with sex-drive issues. But after posting on a psychologist list service, she found that men were the ones seeking help — and willing to pay $150 per hour for her time.

There were the common ailments: sex addiction, erectile dysfunction, sexual anxiety, chronic womanizing, jealousy, porn addiction; the list goes on.

She chronicles the secret and sordid lives of the men she saw — and treated — in her new book “The Men on My Couch” (Berkley), out tomorrow.

The Ph.D. psychologist shared with The Post some of her more titillating composite case studies:

PAUL, THE ‘NON BEING” LOVER

A bank executive in his early 40s, Paul was deeply in love with his new wife. She was sexual, challenging and exciting.

Despite this recipe for relationship success, Paul couldn’t make it happen in the bedroom.

“I’m having trouble keeping it up,” he told her. “So I’m having sex with prostitutes. I’ll give you five sessions to fix this.”

Engler discovered the “blustery alpha male” needed sex without expectation, or as he put it, sex with “non-beings,” to perform.

This is fairly typical of New York men who have illicit options at their fingertips, Engler said.

Erectile dysfunction was “the most common complaint” that she’d heard. And “many of the men who were visiting massage parlors did have some sort of sexual dysfunction . . . with the women that they were actually interested in.”

They got performance anxiety when it was someone whom they cared about pleasuring, or would judge them for it.

Engler gave Paul some “homework assignments” — she told him to caress his wife without aiming for “completion.” She pushed him to enjoy the present moment and forget about an end goal.

But his wife rebuffed his efforts, went rigid and insisted that she was “too tired.” And he stopped attending therapy.

“In the end, it was Paul who had become the ‘non-being,’ ” she wrote.

DAVID, THE NUMBER GATHERER

David, one of Engler’s first patients, seemed to have it all: He was a successful hedge-fund manager with a loft in TriBeCa and a model girlfriend.

“My girlfriend is absolutely gorgeous,” he bragged. “She’s tall and blond, a model with a perfect rack and rock-hard abs.”

But it wasn’t enough.

Nights were spent in clubs pursuing phone numbers from all available women. Sometimes he would sleep with them — most of the time he wouldn’t even call them.

“It’s exciting, like winning a game,” he boasted to Engler. “There’s a process to it, and I’m known for being the best.”

Engler recognized his type immediately.

“I get a lot of narcissist bankers like that, who boast to me about how gorgeous the models are and how young they are. Everything is measured by how the outside world sees him,” she said.

Often, David enjoyed the challenge of getting a phone number more than the actual sex.

Engler broke down David’s cocky facade bit by bit — the final straw was discovering that his cuckolded model girlfriend was actually cheating on him.

Eventually, after months of therapy, David ended it with his girlfriend, moved to Brooklyn and took up playing the guitar.

“What I learned from David is that when men cheat, it’s often psychological, not physical,” Engler said. “A man can be with the sexiest, most beautiful woman on Earth, but it will still not be enough.”

ALEX, Mr. TOO NICE GUY

Kasha and Alex started couples therapy because the sex had become monotonous. Alex, a research scientist, had noticed Kasha seemed disengaged in bed. “It’s like having sex with a mannequin,” Alex griped.

But Kasha had a secret — she was cheating on Alex with a sexy Russian man.

Though Kasha was attracted to Alex’s brilliant mind, she was no longer sexually excited by him. The more Alex tried to please her, the more awful it became, because it seemed like he was trying too hard.

“I’ve seen so many examples like this. Alex is the quintessential nice guy. He doesn’t know how to keep himself and his woman sexualized,” Engler said. “I saw this all the time with my male clients: They learn some skills, but they don’t have the chutzpah — self-possession and courage — to pull it off.”

Engler’s goal became to teach Alex how to change his attitude. He had to search within himself and find a sexual being there. Like a good pupil, he heeded her advice and even anonymously sent his wife a little black dress with instructions to meet at a local hotel.

It worked — at least for a night — but the couple quit attending sessions shortly after.

She doubts it ended well because being “too nice” is often a death knell for a relationship.

“Young and handsome men — accomplished in almost every way — are coming to me nervous about being around women,” she said. “They desire to please us, to perform for us, but have deep fears about what we really think about them. I was surprised at how many of my male clients were anxious to the point of dysfunction over their desire to satisfy a woman.”

OSCAR, THE SERIAL CHEATER

Oscar, a building contractor and an unapologetic “guy’s guy,” openly admitted in group therapy that he was cheating on his wife with a younger woman, whom he employed as his personal assistant.

He boasted to the group: “She’ll do anything sexually.”

Engler at first found it difficult to sympathize with the serial cheater, but upon further inspection she realized there was nuance beneath the bluster.

He felt impotent in his relationship, he revealed. He perceived his wife as smarter, and her family was richer than his.

“My wife makes all the decisions around the house. I know it’s because I’m never home, but I feel useless when I’m there. I’m just a paycheck to her. I feel like she doesn’t appreciate anything,” he told Engler.

Appreciation was the key word.

“The number one complaint from men about women in long-term relationships is, ‘I don’t feel appreciated,’ ” Engler told The Post. “Men are looking for some expression that they are valued.”

When it comes to the bedroom, that often means just being interested. Men care less about their girlfriends gaining weight than women think, because sexiness isn’t about how someone looks, “sexiness is to show interest in sex.”

Oscar eventually decided to break things off with his wife — only to be left two days later by his young paramour.

CASEY, THE PORN ADDICT

Casey considered himself an enlightened soul. His mother was a feminist and he spent his days as a professor.

Still, every night like clockwork, he’d log on to his computer and download porn. The dirtier and more degrading, the better.

These porn stars were nothing like his girlfriend, Amy, a woman he called “a porcelain doll.” Their love was “routine and vanilla” but they were madly — respectfully — in love.

So why did he need nightly smut-fests?

“I’m seeing this in a lot of men I treat,” Engler said. “They feel like they can’t be their authentic selves around the women that they are in love with. But guys who feel this way will find outlets somewhere.”

For these men, pornography feels “safe” because “there’s no judgment, no rejection.”

There are men she treats now that have never known a world without Internet porn — and this online obsession, what she calls “a false eroticism,” distorts and addicts its viewers. The common themes of “power and anger” are “particular” and “deliberately appeal to a man’s most base motivations.”

So to combat his online obsessions, Engler asked Casey to access his own imagination and bring his girlfriend to therapy to find a meeting point between his dark desires and his virginal view of his lover.

After time, “He had much less interest in his nightly porn habit,” Engler writes.

MARK, THE SECRET SADIST

Mark allowed himself to be bullied at his work as a magazine staff writer. Women walked all over him, if they noticed him at all.

He was ingratiating, apologetic, the kind of guy a girl would give up on after the second date because he was boring.

But in private and in the safety a Midtown dungeon, another side to Mark emerged. There, he would hire prostitutes and “torture” them.

“He feels dominated, powerless and trapped by the women in his life, and he is full of rage about it,” Engler says. “So it busts out in his very compartmentalized sex life.”

It took an entire year for the two to reconcile Mark’s sadistic urges with his everyday life.

Using Gestalt therapy, he worked through some of his mommy issues (his father had died when he was young and his mother fell apart) and began to be more powerful in his nonsexual life.

But Mark taught her a valuable lesson about the so-called “good guys” of Manhattan.

They “are high on the profiles of men who go to sex services,” she told The Post.

“There’s something wrong with their ability to be real and authentic. And they’re going to find a way to deal with their frustration elsewhere.”