The TV star announced he was suffering from the condition last Sunday, revealing at one point he lost 60% vision in his right eye.
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And he dropped a further bombshell when he appeared on his mother Sharon's The Talk series in America, claiming he was dropped from an unnamed reality series over fears about his diagnosis.
He said: "I had just booked a job right when I got diagnosed and unfortunately the company that hired me didn't think I could actually perform the job. Out of everything, that's what ticked me off the most, because it's like, 'Don't tell me what I can and cannot do!'"
And his furious mother revealed the company fired him via email.
She tweeted, "They said he was a liability and were so personable, sent an email to let us know."
Despite the career setback, Jack is confident he will win his battle against multiple sclerosis thanks to medical advances.
He told Piers Morgan's CNN show: "I've been told by all my doctors that if you are going to get MS, now is the best time to have it. There are, I think, two or three new drugs coming out within the next six months. I do believe there will be a solution in sight in my lifetime."
> CELEB PICS OF THE DAY
Celeb Pics Of The Day
Celeb Pics Of The Day(01 of14)
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Billie Faiers and Sam Faiers of "The Only Way is Essex" arrive at Las Vegas' Mccarren International Airport Las Vegas (credit:WENN)
Celeb Pics Of The Day(02 of14)
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Christine Bleakley and Frank Lampard share a kiss, Frank celebrates his 34th Birthday today Royal Ascot at Ascot (credit:WENN)
Celeb Pics Of The Day(03 of14)
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Lana Del Rey shopping in Milan's fashion district Milan, Italy (credit:WENN)
Celeb Pics Of The Day(04 of14)
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Hugh Jackman and his family spend the day at the beach. Barcelona (credit:WENN)
Celeb Pics Of The Day(05 of14)
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Lily Cole at the BT ArtBox held at the Dorchester hotel to raise money for ChildLine's 25th anniversary. London (credit:WENN)
Celeb Pics Of The Day(06 of14)
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Kylie Minogue exits Dolce & Gabbana on Rodeo Drive in Beverly Hills. Los Angeles (credit:WENN)
Celeb Pics Of The Day(07 of14)
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Justin Bieber 'The Late Show with David Letterman' at the Ed Sullivan Theater - Arrivals New York City (credit:WENN)
Celeb Pics Of The Day(08 of14)
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Dev Patel HBO's "The Newsroom" Los Angeles Premiere at Cinerama Dome Los Angeles (credit:WENN)
Celeb Pics Of The Day(09 of14)
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Rihanna leaving a recording studio late at night London (credit:WENN)
Celeb Pics Of The Day(10 of14)
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Laura Whitmore Lacoste - Flagship Store Launch Party - Departures London (credit:WENN)
Celeb Pics Of The Day(11 of14)
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Tara Reid shopping in Milan's fashion district Milan, Italy (credit:WENN)
Celeb Pics Of The Day(12 of14)
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Penelope Cruz The Cinema Society With The Hollywood Reporter & Piaget and Disaronno screening of 'To Rome With Love at the Paris Theatre New York City (credit:WENN)
Celeb Pics Of The Day(13 of14)
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Matt Cardle, at Dean Piper's birthday party at the Wellington Club London (credit:WENN)
Celeb Pics Of The Day(14 of14)
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Andrew Garfield, Emma Stone and Rhys Ifans at the German premiere of "The Amazing Spider-Man" at Cinestar Sony Center movie theater at Potsdamer Platz square in Mitte. Berlin (credit:WENN)