Osbourne, 26, who welcomed daughter Pearl with his fiance Lisa Stelly in April, was given the news of his diagnosis two weeks after his daughter's birth.
"I was just angry and frustrated and kept thinking, 'Why now?'" Osbourne told People. "I've got a family and that's what's supposed to be the most important thing."
Multiple Sclerosis is an autoimmune disease that affects the central nervous system - the brain and spinal cord -- and can affect muscle control, strength, vision, balance, thinking and feeling.
Osbourne, the youngest of Ozzy and Sharon's three children, shot to fame as the rebellious teenager alongside his sister Kelly in the MTV reality TV show "The Osbournes" in 2002, a fly-on-the-wall series following Ozzy and his family on their day-to-day lives.
The young star, who has been in rehab for drug abuse in the past, cleaned up his act and starred in his own show in 2005, "Jack Osbourne: Adrenaline Junkie," which saw Osbourne undertaking various extreme sports around the world.
