Shannen Doherty and her husband Kurt Iswarienko married in October 2011 and she was diagnosed in 2015
Credit: Angela Weiss/Getty

Shannen Doherty is fighting the toughest battle of her life, but she isn’t fighting alone.

The actress credits her husband, photographer Kurt Iswarienko, for standing by her every step of the way during her battle with cancer.

“My marriage was always strong, but it’s made my marriage a thousand times stronger,” Doherty says in a preview of Tuesday’s episode of Entertainment Tonight. “I could not have gotten through this without my husband.”

Later in the episode, she said: “I told him, ‘You need to enjoy every single second you have with me because I’m going to be dead in five years,’ and he just burst out in tears. Thankfully, that phase was short.”

The couple married in October 2011 at a private estate nestled in the hills of Malibu. Doherty, 45, learned of her breast cancer diagnosis in March 2015, which she exclusively revealed to PEOPLE last August.

“I called him, which was horrible of me,” Doherty says of the time she broke the cancer news to him. “I was in the car. I was with my mom, and the doctor called me and I’m, you know, ‘I’m going to wait until I see him,’ and I just couldn’t. So I picked up the phone and I called him and he was like, ‘Where are you?’ ”

When she arrived home, her husband was waiting for her in the driveway.

“[He] hugged me and said, ‘We are going to get through this. You are going to be okay,’ ” she recalls. ” ‘We are going to get through this, you’re strong and you’re powerful and you’re not going anywhere. You have so much to do in your life. We are going to get through it as a family.’ ”

Doherty also spoke about the impact her

mother has had on her life.

“Thank God I have her and thank God she is there,” the actress says. “She is so strong, and my mom is like a steel magnolia. She is a Southern girl, and she puts on this very strong face with me. She is constantly looking stuff up and, you know, she will force-feed me Gatorade chips.”

“Her and my husband tag team. It’s amazing,” she adds. “They’ve really come together to take care of me.”

Doherty’s three-part Entertainment Tonight interview continues on Tuesday (check local listings).