Credit: Michael Buckner/Getty Images for Activision Photo: Jack Osbourne at the First-Ever Call of Duty XP on September 3, 2011 in Los Angeles

Jack Osbourne and his fiancee Lisa Stelly had their first daughter together just a few weeks ago, so this should be a period of total joy for them — but with shocking news breaking regarding Jack's health, their family life is set to get much more complicated. In a dramatic new interview with PEOPLE, Jack Osbourne has revealed that he was recently diagnosed with multiple sclerosis, a central nervous system disease that can cause serious disabilities. 

"I was just angry and frustrated and kept thinking, 'Why now?' " Jack explained. "I've got a family and that's what's supposed to be the most important thing."

A lengthier interview with Jack and his mom, Sharon Osbourne, is due out in this week's issue of PEOPLE.

Source: PEOPLE