"I was still a virgin when I met him," Thompson tells ET's Nancy O'Dell during an intimate sit-down to discuss her new memoir, A Little Thing Called Life: On Loving Elvis Presley, Bruce Jenner, and Songs in Between. Presley and Thompson met in Memphis on July 6, 1972, when she was 22.
"I think that is what added to the allure of me for him," she recounts. "Because he was a very territorial man. And a very jealous man. It really made him feel wonderful that I was a virgin."
Losing her virginity to the "Hound Dog" singer "made him more special," Thompson says, adding, "As if Elvis Presley could have been any more special."
Presley had actually been special to Thompson as far back as childhood, when she told her parents that she'd one day marry the legendary singer when she grew up.
"When I was six years old, sitting at the breakfast table, I [told my parents], 'I am going to marry Elvis Presley,'" Thompson remembers.
While she never walked down the aisle with the music superstar, she did end up dating him for over four years, eventually splitting up in 1976, eight months before Elvis died of a heart attack. During that time, Thompson says she learned a lot about The King that she never expected.
"I saw prescription medication on his nightstand," Thompson says, "and when I questioned, 'Have you been ill?' He stammered and he didn't really have a good answer for it."
"I had never been around drug abuse or alcoholism, my parents didn't even keep alcohol in the house, not even beer," she adds. "I was pretty green going in."
While the prescription pill abuse got worse over the course of their relationship, Thompson says Presley started cheating on her as well, and frequently.
"Elvis was not monogamous. As we say in the South, bless his heart. He just wasn't monogamous," she says. "He had a tremendous capacity to love and he loved women and women loved him… I was happy to share him with his legions of fans and even understood sharing him occasionally to infidelity, but it didn't make it any easier."
"I didn't think that lifestyle would be conducive to family life," she recalls. "I had to make a decision. It was a tough one and I felt depleted once I left."
Before calling it quits with the rock 'n' roll legend, Thompson says she had a prophetic moment about her future relationship with Jenner, similar to her youthful declaration that she'd one day marry Presley.
"Elvis and I were sitting in bed watching the 1976 Olympics from Montreal and this incredible visage of a man, this incredible specimen of man crossed the finish line of the decathlon," she shares, recounting Jenner's triumphant Olympic performance. "Elvis turned to me and said, 'You know, I am not gay, but that man is a damn good-looking man,' and I said, 'He is. In fact, I think one day I am going to marry him,' and Elvis said, 'Yeah, over my dead body.'"
"So it's an insanely crazy moment that, you know, of course I couldn't of had any portent of what was to come," she adds.
Four years later, in 1980, Jenner and Thompson sparked a relationship that lead to them tying the knot in 1981 and welcoming two children, Brandon and Brody Jenner. They would eventually divorce in 1986.
Five years after that relationship ended, Thompson hit things off with yet another icon: music producer and recording star David Foster.
"He's one of the funniest people that I have ever met and he is charming," Thompson marvels. "He had this raucous sense of humor, an irreverent sense of humor, and I hope he's forgiven me and the hurt that I have ever caused him."
Foster and Thompson filed for divorce in 2005, 14 years after they tied the knot and six years before he would go on to marry Real Housewives of Beverly Hills star Yolanda Hadid.