It's been three years since they pulled the plug on their marriage, but Pete Wentz is just opening up about what exactly went wrong in his marriage to Ashlee Simpson.

In an interview this week with Howard Stern, the Fall Out Boy Rocker opened up about the couple's divorce, revealing for the first time just where things went wrong for them.

According to the rocker, things first started falling apart when his band went on a hiatus in 2010-which changed how he saw himself.

"At 31, we'd had all these great years as a band, and then we took time off, and I basically became Mr. Mom," he said. "I had the beard, the flannel shirt. I didn't know what my identity was. That factored in. When your identity is what you do, it's hard when you stop doing it."

"It was the first time where I was like, 'Well, no one's really taking my picture. I'm just basically hanging out with my kid all day. Who cares? I think when you stop caring about your personal appearance, your personal hygiene, it makes you even more depressed, but it makes you do it more," Wentz added. "It's like a vicious cycle."

In addition to his losing his identity for a while, Wentz claims that the fact he and Simpson married so young-at ages 29 and 24-they weren't really prepared for the hardships of marriage-which helped cause their relationship to fail as well.

'I think there's an important thing where you know how to fight, because you ca fight with somebody and it's not the end of everything," he said. "But if you don't know how to have those arguments, then they become nuclear. And we were doing this all in the public eye, which doesn't help."

The pair have since become friends and co-parent their son, Bronx, together.

They have also both moved on from their divorce-Wentz and girlfriend Meagan Camper welcomed their own son, Saint Lazslo in August 2014, while Simpson married Diana Ross' son, Evan Ross that same month. They have also since announced that they are expecting their first child together.

Tags: Pete Wentz Ashlee Simpson