The actress, who just married her fiancé of almost three years, pro baseball player Cutter Dykstra, opens up to PEOPLE in this week's issue about her battle with multiple sclerosis (MS), which she was diagnosed with at 20 years old.
"I wasn't ready until now," Sigler says of revealing her illness. "You'd think that after all these years, somebody would be settled with something like this, but it's still hard to accept."
Though the Sopranos alum, 34, initially went symptom-free "for quite some time," the disease, which damages the central nervous system, "reared its ugly head" over the last decade. "I can't walk for a long period of time without resting. I cannot run. No superhero roles for me," she says, laughing. "Stairs? I can do them but they're not the easiest. When I walk, I have to think about every single step, which is annoying and frustrating."
Working over the years after The Sopranos ended meant covering up her illness. "Sometimes all I needed was like five or 10 minutes to sit and recharge but I wouldn't ask, because I didn't want them to be suspicious," she says. While MS has no cure, Sigler has "run the gamut" with MS drugs including injections and infusions and now takes the twice-daily pill Tecfidera, which has kept her symptoms stable for the past six years.
"Things are manageable now," she adds. "It takes a fighting attitude to deal with all this. This disease can absolutely take over your life if you let it."
"I'm at a point in my life with my son, with my new marriage, it's a new me. I don't want to hold a secret where it feels like I have something to be ashamed of or have something to hide," she tells PEOPLE. "It's part of me, but it's not who I am."
The actress also felt it was important to speak the truth for her son's benefit. "I didn't want him to get to an age where he felt like he had to keep this secret for me as well," she adds. "I wanted to be an example to him of strength and courage."
As for her recent wedding, Sigler believed walking down the aisle was like "walking into a new life."
"I don't know what's to come. But I'm excited for the first time in a long time," she says. "I've got my brain and my heart and I've prepared myself for everything that could happen. But I've got an amazing husband, the best son, and I hope that we can make more babies and just keep having fun. I'm the luckiest girl in the world."