Kourtney Kardashian has been putting on a brave face, but a source tells People magazine that she is heartbroken. "Kourtney is miserable at the moment, so miserable," the source said to People of the "Keeping Up With the Kardashians" star.

Kardashian has been focusing on her three children since the breakup. She recently let Disick spend time with their eldest child, Mason, 5 on Wednesday. The father-son duo was spotted together at a Barnes & Noble in Calabasas, Calif. where they loaded up on toys, reports TMZ. The site says that although Disick has been out of the picture for the past month following his split with Kardashian, he kept in touch with his children mostly through FaceTime.

Kardashian is supposedly seeking sole custody of the couple's three young children. The reality star has been recently seen going into a Century City office building in Los Angeles. It is presumed that she paid a visit to the office of Laura Wasser, a celebrity divorce attorney who has represented both Kim and Khloe Kardashian in their divorces.

The couple of nine years split after Disick was spotted getting close with stylist Chloe Bartoli during a vacation in Monte Carlo earlier this month.