While Justin Bieber may have been gone back to Hailey Baldwin, Kourtney Kardashian has also gone back to what she does best -- parenting!

The sexy mom carried one-year-old son Reign Aston while donning a pair of tight leather pants and a white faux fur jacket. The mom of three took her son to a playdate in Beverly Hills on Thursday. And we have to say, despite holding her adorable son -- the mom does not look happy. But we can't blame her -- her former boytoy has a new lady AND is talking about his fling with the 36-year-old.

We wouldn't be happy if the Biebs said we were using him either! In an interview for The Bert Show that aired last night, the 21-year-old said told the host, "I’m being used, man. What can I say?"

Apparently Kourt is NOT happy about the interview or the fact that their relationship was leaked in the first place.

An insider told Hollywood Life, “Kourtney wants a major explanation and apology. She’s not the one who leaked their romance to the public. She feels like she’s being punished and it just goes to prove her initial instinct -- that Justin is too young and too immature for her. She’s kind of beating herself up for ever getting involved with him in the first place, and not listening to her gut. She really regrets the whole thing."

Doubtful! We bet she only regrets getting caught!