Jack Osbourne has had symptoms of multiple sclerosis for "three or four years".
The 26-year-old star was diagnosed with the autoimmune disease - which affects the central nervous system - five weeks ago after suffering vision loss in his right eye but has now realised he was showing signs of the condition for some time prior to his doctor's assessment.
He said: "I guess I've been having symptoms for the last three or four years, but I didn't realise it.
"I had problems with my bladder, problems with my stomach and then, about two years ago, my legs went numb for two months and I just thought I had pinched a nerve."
Despite suffering from vision loss, Jack - who was diagnosed just two weeks after his fiancee Lisa Stelly gave birth to their daughter Pearl - says he has now regained "about 80 per cent" of his sight back, though he doesn't know whether it will completely return.
He said: "They don't know if it will ever improve beyond that, but everyone's different.
"[My vision] will return to some capacity but like I said, everyone is different, some people are left with a blind spot, some people return a 100 per cent, some people never even get anything back, so it's hit or miss."
The 'Adrenalin Junkie' host insists he is currently feeling good but knows the nature of his condition means that could change at any time.
Speaking on The Talk - on which his mother Sharon Osbourne is one of the presenters - he said: "Honestly, I'm fine. [But] one minute you can be fine and the next, I went blind in my right eye. It's a completely unpredictable disease."
And Jack admits becoming a father has meant he doesn't have time to dwell on his illness.
He said: "It's been good because I haven't had time to be like, 'Oh, I have MS,' because I have to change diapers and stop the baby from crying."