Singer David Cassidy is speaking out further on his dementia diagnosis, which he recently revealed.

“When friends of yours or family members begin to say to you, ‘Remember I just told you this two days ago,’ and there is no memory of it, that’s when I began to be very concerned,” the former teen heartthrob, 66, says in the episode of “Dr. Phil” scheduled to run Wednesday.

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Despite at least two DUI charges and a stint in rehab over the past few years, Cassidy said he was not impaired when he fell onstage, slurred words and had trouble remembering lyrics during a Feb. 18 concert at The Canyon club in Agoura Hills, California.

“When you have spotlights in your eyes, and you’ve had five eye surgeries, as I’ve had — and I’ve talked a lot about it — you see me there, I tripped on that [stage monitor],” he told Dr. Phil McGraw, referring to the incident caught on video. “But I certainly wasn’t intoxicated and it has nothing to do with why I’m leaving [show business].”

He added, “Certainly, my dementia has contributed to the reason why I don’t want to go out and I don’t want to hear, ‘Well, he looked like he was drunk’ or ‘He looked like he was . . . ’ ” he said, his voice trailing. “I wasn’t.”

Cassidy — who gained famed in the 1970s musical sitcom “The Partridge Family” and hit songs such as “I Think I Love You” — has a family history of dementia, McGraw told “Today” on Tuesday, explaining, “His grandfather died of dementia. His mother died of dementia.”