By Chloe Melas, CNN

(CNN) -- Chrissy Metz says she suffered years of physical and emotional abuse by her stepfather when she was growing up.

Metz, who stars on the hit NBC series, "This Is Us," opened up about her past in a new memoir.

"I don't remember why Trigger hit me the first time," Metz wrote, referring to her stepfather in "This is Me," which will be released on March 27. "He never punched my face. Just my body, the thing that offended him so much. He shoved me, slapped me, punched my arm. He would hit me if he thought I looked at him wrong."

Metz spoke to People magazine exclusively for its April 2 cover story, saying "I'm a tough cookie, but it's one of those things that attempts to break your spirit."

The 37-year-old actress recounted in the book an incident in which Trigger pushed her to the floor.

"I was begging to know what I did," she wrote. "He just shoved me hard with his foot." People.com published excerpts from the book and Metz's interview on Wednesday.

She believes he beat her because she was overweight.

"My body seemed to offend him, but he couldn't help but stare, especially when I was eating. He joked about putting a lock on the refrigerator," Metz wrote. "We had lived with a lack of food for so long that when it was there, I felt like I had to eat it before it disappeared. Food was my only happiness."

Metz says it was around this time that she began to hide her eating habits.

"I'd get up in the middle of the night and eat. I'd sneak food to eat in the bathroom," she wrote. "Cookies, chips. Things I could eat as fast as possible to avoid detection. Things that would give me the brief bliss of numbness."

Metz's story does have a happy ending, however. She said that she has a relationship with Trigger and that she does "care about him." The abuse she endured has only made her a better person, she said.

"We all go through stuff. But I truly believe that everything that happened to me, happened for me," she wrote. "[I've learned] some beautiful lessons."