Kim Kardashian had a really bad case of COVID-19 along with her kids, which shut down production of her show for 2 weeks ... and she says it disrupted her studying for her second crack at the baby bar.

A teaser for "Keeping Up with the Kardashians" already revealed Saint had tested positive for the virus -- but on Thursday night's episode we find out the health crisis went far beyond her oldest son, and affected her whole brood.

Kim says Saint tested positive after an apparent outbreak at his school, and she was really worried about him because he was crying and coughing a lot ... on her. Of course, with 3 other kids in the house, she was also concerned about it spreading, and that's exactly what happened.

North started feeling sick soon after, and eventually both she and Kim discovered they had COVID too. At that point, producers decided to shut down all 'KUWTK' shoots for 14 days while the family quarantined.

Kim says she had some severe symptoms, like a 104-degree fever ... exactly when she was supposed to be putting in 12-hour daily study sessions to retake the baby bar exam -- which as we reported, she'd previously flunked.

Fortunately, everyone in the fam recovered okay, but it seems Kim failed on take 2 of the test. Earlier this week, she said she was studying to take it again.

It's still unclear exactly when COVID hit Kim and her kids since the show was filmed months ago, but we know Khloe contracted the virus sometime in 2020 and revealed on 'KUWTK' that her symptoms were so bad ... Kris Jenner called every doctor she could think of for help.

Kim previously stated Kanye West also had it in the very early days of the pandemic.