Lena Dunham reveals she cheated on ex Jack Antonoff with childhood boyfriend

Lena Dunham revealed in her new memoir that she cheated on Jack Antonoff with an old flame from her childhood.

Dunham candidly writes about the end of her and Antonoff’s relationship in “Famesick,” which released Tuesday. The “Girls” creator, 39, and the music producer, 42, dated from 2012 to 2017.

Dunham writes that she and Antonoff were not in a good place in their relationship after she got a hysterectomy in 2017 and was quickly becoming more dependent on medication.

During the low point in her and Antonoff’s relationship, Dunham reached out to a man named Nick, whom she describes as her former middle school boyfriend that she had kept in touch with over the years.

After telling Nick one night that she wanted him to cheer her up after surgery, the two met up and she asked him to sleep with her.

“In the cab, we hugged again, and I said this: ‘I’ve been through something awful. I don’t want to talk about it, but I need you to f–k me and I need you to do all of the work.’”

Dunham recalls the two of them then having sex, writing, she felt a “euphoria that in recent months only intravenous medication had provided.”

“It wasn’t a sexual pleasure really … but I had complete thoughts for the first time in months,” she continues. “They sounded something like this: I am an adulteress. I am a c–t. My intestines are where my womb should go, but look at this, I am alive.”

Dunham continued to sleep with Nick while Antonoff was away on tour. Eventually, she says she couldn’t ignore that she and Antonoff needed to break up.

She recalls sobbing while telling Antonoff one morning over breakfast that they both knew they weren’t making each other happy anymore.

She says he agreed and they both cried, telling each other they were each other’s first great love.

“We put our foreheads together and wept. In some fit of delusion, I asked if we could still go on dates,” she writes. “‘We can do whatever you want,’ he said, the relief making us both euphoric with adoration.”

Dunham’s rep confirmed her breakup from Antonoff in January 2018 after five years together, telling Page Six at the time that the split was “amicable.”

Dunham — who also detailed her “Girls” co-star Adam Driver’s alleged on-set outbursts — and Antonoff are now married to other people.

Dunham married musician Luis Felber in September 2021, while Antonoff married actress Margaret Qualley in August 2023.