Buffalo Bills Player Reveals Why He Proposed to Terminally Ill Girlfriend: 'I Wasn't Going to Let Fear from Cancer Stop Me'

Tony Steward was determined to make Brittany Burns his wife.

"I wasn't going to let fear from cancer stop me from doing what I wanted to do," the 23-year-old Buffalo Bills linebacker tells PEOPLE in his first interview since his fiancée died of cancer earlier this month. "Britt means the absolute world to me and we truly believed that we were just going to beat this and we were all going to move on with our lives."

Steward and Burns' family were all shocked when the 26-year-old died on Feb. 1. The two were engaged for less than two months when she suddenly succumbed to a rapidly-progressing, rare form of ovarian cancer.

But the NFL star says he cherishes the years he spent with his college sweetheart-turned fiancée.

"Every single day was an adventure with her and just really being able to have something like that is unbelievable," he says. "It's amazing because a lot of people never even get to experience that in life and I got to experience it for four of the greatest years of my life.

"I wouldn't have it any other way."

Although still coping with Burns' death, Steward says he, along with Burns' family, are throwing themselves into " Tony & Britt's Fight Like a Girl Campaign" – a charity the two began to fund ovarian cancer research.

He says that Burns would want him and her family to move forward and "make a difference." He and Burns' family have been active in fundraising, campaigning and raising awareness about the disease, which Burns' mother calls a "silent killer."

Burns and Steward both attended Clemson University, where he played football and she was on the women's rowing team. He recalled first meeting her during his freshman year of college.

He says she waltzed into one of his classes sporting purple hair in an effort to raise money for a volunteer trip to Vietnam.

"I just stared at her hair because I thought it was pretty cool and I guess I was staring a little too hard because she looked at me and asked me if I had a problem," Steward tells PEOPLE. "I was so embarrassed. I was just like, 'No, I don't have a problem, but I like your hair.' And she just walked out of the room."

He says he had another encounter with Burns after donating to her trip fund, and the two began dating a few months later.

"These last four years of my life have been the best four years of my entire life. She brought out the best version of me that I didn't even know was inside of me," he gushes.

"If I could have – if the situation was right – I would have proposed to Britt a couple months after we started dating. That's how in love I was."

Burns' health issues began last October, when she went to a doctor complaining of stomach pains and fatigue. Officials initially thought she simply suffered from a few ovarian cysts, but during a surgery to remove them, doctors found a tumor.

Her family says that multiple hospitals confirmed Burns' rare cancer, a combination of carcinoma and mixed germ cells.

Still, Steward says he always expected Burns to beat the illness. In the midst of her health battle, he looked forward to spending the rest of his life with her.

Burns' father, Ty, recalls the phone call from Steward.

"I could tell he was really nervous and really upset. I said, 'Are you okay?' And he said, 'I wanted to ask you if it was okay if I asked Britt to marry me," Ty tells PEOPLE. "I could tell that was a big relief. I could say that it was one of the few times I can truly say that I saw Tony nervous."

He proposed to Burns in December – just days after she was diagnosed – at a restaurant in Philadelphia, surrounded by Burns' family.

A friend of Burns previously told PEOPLE that Burns tried to plan the wedding while undergoing chemo, but she was always too sick.

Steward says he still can't believe that Burns is gone and is coping as best he can.

"The only thing that we can do is know that she's in a better place and continue to live our lives because she would not let us sit around and sulk," he says.

"We're going to make sure that we live the way lives should be lived, how Britt lived her life. She's going to live on through us."