Jack Osbourne knew something was wrong last month when his vision was failing him.
"I couldn't see anything in front of me," Osbourne, 26, tells PEOPLE in this week's cover story. But when he sought medical help for that problem, he received a shocking diagnosis
Multiple sclerosis was to blame for his vision loss – 80 percent in his right eye. He's now beginning medication and adopting a healthier diet regimen to help reduce symptoms of the disease, which attacks the brain and spinal cord and can affect vision, movement and cognition. And luckily, his vision has also improved. "It's just one of those things you take as it comes," says Jack. "It's all about your outlook."
Just weeks after receiving the news, Jack and his mother Sharon opened up in an emotional interview with PEOPLE at Jack's parents' home. Says Sharon: "The first thing Ozzy and I asked ourselves was, 'What did we do wrong?' "
Despite the initial devastation, the entire Osbourne clan is determined to maintain positivity
, especially Jack, who is optimistic about his prognosis. "My life is far from over," he says.
"I was very sad and totally in shock," Jack's father Ozzy tells PEOPLE. "[But] I've got to tell you, he's handled it much better than I would have. He's a very strong kid."
Adds Sharon: "Osbournes survive everything. We really do."
For all the details of Jack's shocking diagnosis, a candid interview with Jack and Sharon, and more on how the famous family is coping, pick up next week's issue of PEOPLE, on newsstands Friday
To get a sneak peek of this week's issue, click here