John Stamos Says He Caught Former Girlfriend Teri Copley in Bed with Tony Danza: 'Worse Than Anything'

Copley denies cheating and says she and Stamos were already broken up

John Stamos claims he caught his former girlfriend in bed with Tony Danza.

In his upcoming memoir, If You Would Have Told Me, Stamos, 60, claims that he walked in on girlfriend Teri Copley in bed with Danza, now 72, while he was dating the model-actress in the 1980s.

The Full House alum describes the incident to PEOPLE as “physically painful” and “worse than anything.”

“I can't explain it, but I would've rather been punched in the nose again or something because the pain is so overwhelming,” he says. “Looking back, it's like, probably, she wasn't the right girl for me. So seeing him, realizing it was him and stuff, it was hard. I mean, it was awful.”

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Stamos says he walked into Copley's guesthouse and found the actress asleep in bed with a man he did not immediately recognize who had “ripped abs.”

Completely “breathless” at the sight, Stamos says he stumbled out of the room backward.

“At first I was like, ‘I'm going to kick his…’ I didn't know it was [Danza] yet. I see his abs. I'm like, ‘Maybe not. F--- it.’ And I ran,” Stamos recalls. “But I remember running down the driveway with tears streaming down my face and I didn't want anyone to see me."

Copley, now 62, maintains her relationship with Stamos was already over at the time of the incident. "I wondered, 'What was John doing there?' because we had broken up," she tells PEOPLE. "He just looked at me and shook his head, and walked away."

In his memoir, the Stamos says he identified the man as Danza only after seeing a poster of Copley she had signed “My Dear Tony" in the front seat of an unfamiliar car parked outside of her home.

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“I jump in the El Co, start the car, and Elton John is still singing, and that’s when it hits me,” Stamos writes in his memoir, according to Entertainment Weekly. “I mouth the words to his most famous lyrics and realize the name of my rival: ‘Hold me closer, Tony Danza. . . .’”

“It took me a long time to get over that," he tells PEOPLE.

Stamos describes Copley as “just a nice person.”

“I mean, it wasn't right to cheat on me, but I was too immature; I wasn't a man,” he tells PEOPLE. “I didn't become a man for a long time and I think she was... I don't know. I was broken.”

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Stamos says he included the alleged incident in his memoir because of its relatability.

“I really wanted to find relatable things that happened in my life,” he says. “Because I think everybody thinks, like, ‘Oh, this guy's got no problems. I'm sure he's never been cheated on.’ ”

When people are cheated on, they “make a list,” Stamos says. “It's like, ‘Oh, she left me because I don't have enough money,’ or ‘I'm not good-looking,’ or this and that.”

“And then you look at me and I go, ‘Well, he had all those things,’ ” he says. “People are s-----. And it's life.”

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The actor also points out that, at least in his eyes, everything “evened out” in the end. Stamos credits Danza's popular show Who's the Boss? with much of Full House’s initial success, as it was its lead-in. Full House became the launchpad for Stamos’ career.

“Back then you go, ‘Life isn't fair.’ And then, ‘Oh, wait a minute. It got evened out,’ ” Stamos tells PEOPLE. “I honestly believe if we didn't follow his show in the summer, that would've been one and done for that show, Full House.”

Stamos adds, “That's a big part of everything too, is sometimes the hardest thing to do is go with the flow. Because if you're a good person, and you treat people well, and [lovingly], you do good things in the world, most of the time, you're going to be okay.”

For more on John Stamos, pick up the latest issue of PEOPLE, on newsstands everywhere Friday, or subscribe here. 

If You Would Have Told Me is available Oct. 24 wherever books are sold.

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