UNDATED (USA TODAY) -- Just two weeks after the birth of his first child, Jack Osbourne was diagnosed with multiple sclerosis, reports People.

"I was just angry and frustrated and kept thinking, 'Why now?' " says Osbourne, 26, who, along with fiance Lisa Stelly, welcomed daughter Pearl Clementine on April 24. "I've got a family and that's what's supposed to be the most important thing."

Multiple sclerosis is a disease that affects the central nervous system.