The singer opened up to comedian Nikki Glaser in a new profile for Interview Magazine, where J Lo confessed her "whole f***ing world exploded" after the release of her musical film, "This Is Me... Now: A Love Story" -- which let her love story with Ben take center stage.

While Jennifer didn't name Ben directly, she hinted at what caused her marriage to fall apart ... telling Nikki, "You have to be complete, if you want something that’s more complete."

Per Jennifer, she thought she had already "learned that," but had a revelation over the summer.

She continued ... "I had to be like, ‘I need to go off and be on my own. I want to prove to myself that I can do that.'"

J Lo recalled feeling a mix of emotions following the separation -- including fear, sadness, and desperation.

She added ... "Being in a relationship doesn’t define me. I can’t be looking for happiness in other people. I have to have happiness within myself."

As for whether she's looking to date again amid the split, Jennifer made it clear she's focusing on herself right now ... noting she was "not looking for anybody."

TMZ broke the story ... Jennifer filed for divorce from Ben in August after separating earlier in the year. Concern for Jen and Ben's marriage grew after the actor moved into his own home this summer ... with the singer staying behind in their marital pad in Beverly Hills.

The couple then tried to unload the residence ... nearly selling the property to a couple from New Jersey, before the deal fell out of escrow.

Jennifer also notably canceled her summer tour amid the marriage woes ... which she now says was for the best.

According to Jennifer, she needed the time to focus on herself and her kids ... calling it the "the hardest time of [her] life."