Kenneth Mitchell has been diagnosed with amyotrophic lateral sclerosis, or ALS, a debilitating neurological disease that slowly takes away a person’s ability to control his or her muscles.

In an exclusive interview with PEOPLE, the Star Trek: Discovery star, 45, opens up about his life-changing diagnosis, how it has affected him and his work, why he hid it for nearly a year and a half, and how he plans to use his platform to help others.

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After experiencing constant twitching in his muscles in the months leading up to August 2018, the actor was led to believe that he was suffering from either a pinched nerve or multiple sclerosis (his mother has MS).

“The moment that they told us it was [ALS], it was like I was in my own movie,” Mitchell says, fighting back tears. “That’s what it felt like, like I was watching that scene where someone is being told that they have a terminal illness. It was just a complete disbelief, a shock.”

“I do remember there was something really simple and beautiful in a way, how my wife and I were in the trenches together, and how we from this moment on we’re having to deal with something so severe that was going to affect our lives forever,” adds Mitchell, who has played multiple roles in Star Trek: Discovery, including Kol and Tenavik. “We grieved and mourned really hard. There was so much unknown.”

Mitchell, who shares daughter, Lilah, 12, and son, Kallum, 7, with wife, Susan, said the diagnosis forced him and his family to shift their focus on everyday life.

Image zoom The Mitchell family

“I think it, over time, became the theme of us accepting this with grace,” he says. “Trying to see the beauty in it, in a way. I’ll never forget, one of my Star Trek costars told me, because they had dealt with some trying times with illnesses and stuff, and I remember them communicating to me, saying, ‘You have a choice. You can look at this in many different ways, but maybe try to look at this like a gift where you get to experience life in a way that most people don’t.'”

“From that point on, it became, ‘Let’s just spend time with the family,'” Mitchell continues. “We took a couple vacations. Pulled the kids out of school. We had meetings with all their schools, with the principal, the counselors, their teachers. Everyone was in support and understanding the situation and that we might be pulling them out of school more than most, just so we can spend some time together as a family while I was still healthy.”

Over the course of the next year and half, Mitchell (who also stars in the CW’s Nancy Drew) continued to work to the best of his ability — but faced some road blocks along the way.

After landing the lead in a television show, Mitchell informed production about his diagnosis and decided to give up his part, as it would require a move to Newfoundland.

“We realized it wasn’t right for me health-wise and emotionally to move away from my family just to go work on this project,” he explains. “That being said, I wanted to see it through. I cared about the people and I cared about the show and the character that I created. Being lead of the show, I really wanted that responsibility. But in the end, it just wasn’t the right thing to continue on.”

As he began to tell people here and there of his recent diagnosis, Mitchell says his acting community came together to offer support in different ways.

Image zoom Lisette M. Azar/CBS

“When I started [Nancy Drew], I was playing a character that was ‘normal’,” he says. “They were aware of my limitations and my illness, but they still wanted to work with me. Although it feels more challenging to play this character who doesn’t have any disabilities, it’s the process that they do. They accommodate and make it work. We use the double, the stunt double, the body double, punching and on closeups, and medium shots with me. Or my shots will be me, the scenes will be me seated or leaning up against something. They just make it work. They do it in a way that they don’t ever make me feel like I’m dragging things out or a hindrance or anything. It always makes me feel like I’m still an asset. That’s really empowering.”

Mitchell says roles have even been created specifically for him.

Image zoom Kenneth Mitchell in Star Trek: Discovery Russ Martin/CBS

“Dan Shotz and Jon Steinberg created this show, The Old Man, with Jeff Bridges and John Lithgow, and they created a part for me,” he says. “An FBI agent and I got to be in this chair. It was just really liberating and freeing to not have to hide what was happening to me. It was at that point forward, I was like, ‘Yeah, I’m ready for this. I think this is the direction I should continue to take.'”

Now, using a wheelchair since October 2019, Mitchell says he’s more than ready and willing to speak his truth.