A source told Radar of the alleged breakup, which is said to have went down on Christmas Day.
"He finally plucked up the courage to tell Kylie he's done, that he loves her and will always be around for the baby, but they're not compatible as a couple," the source said. "Kylie was totally blindsided even though everyone else in her life saw this coming."
The 25-year-old rapper reportedly said he "can't do this anymore," in reference to wanting to maintain his normal lifestyle of partying and touring.
As for how Jenner has reacted, she's reportedly still trying convince the "Goosebumps" rapper to stay with her and raise their child as a couple.
"She's still refusing to admit it's over, and begging him to stick around," the source said.
The couple have been dating since April, with the couple reportedly conceiving a child together over the summer.
The couple still have not confirmed the pregnancy and have not addressed any breakup rumors.