"When I came out in February, it actually wasn't the time I wanted to come out. I was going to come out to my [pro] team – whoever drafted me," he said in an interview prior to his historic May 10 selection by the St. Louis Rams, speaking to PEOPLE exclusively for a portfolio of gay professional athletes on their choices to play and live openly.
(Watch our video featuring five pro gay athletes sharing their moving stories below.)
Well before his announcement – which eventually made him the NFL's first out gay player – his sexuality was already known in Sam's college town of Columbia, Missouri, and among his University of Missouri teammates, whom the 6'2" defensive end informed last fall at the start of his senior season.
"They knew they could tell whoever they wanted to, but they didn't," Sam, who grew up in Hitchcock, Texas, said. "They kept it secret. They didn't have to. I was out. I did my own thing. I had my boyfriend" – Vito Cammisano, a former athlete on the Missouri swim team.
"When I came out in February, I did it because when I participated in the Senior Bowl, I was surprised how many people in the media knew. Everyone who did an interview with me said, 'Okay, we know you're gay, can we break the story?' So I said okay, and I called my agent," he said. "The rest is history."
While he must still earn a playing spot on the Rams' roster, Sam's draft marks a new era for the NFL, and he hopes for the same supportive environment he knew as a college player.
"I'm probably one of the few to be as blessed as I am, to have great teammates the way I did, and have the great coaching staff the way I did at Mizzou," he said. "Everyone in that program was so respectful of me, I wanted to give them all I got."
"I always knew I was different. I knew I had a male attraction probably in 7th grade," he said, "but I didn't act upon it. I didn't act upon it in high school. But college was different. College is all about experimenting. I did, and then I was like, 'This is who I am.' "
With his new Rams jersey quickly becoming the No. 2 seller among NFL rookies, Sam's status as a role model "hasn't hit me yet," he said.
"I'm excited about this process. I'm excited to be here."
For more on Michael Sam and the exclusive portfolio of gay professional athletes, pick up this week's issue of PEOPLE, on newsstands now
Reporting by MARY GREEN