Adult film star Kylie Page struggled with substance abuse in the years leading up to her shocking death — but had celebrated a sobriety milestone days before she took her last breath.

Kylie’s struggle with addiction was no secret, as family sources tell TMZ she had dabbled in drug use since she was a teen. However, she went to rehab a few years back and subsequently lived in a sober living house … and we’re told the combination of both did wonders for her mindset and life trajectory.

Our sources say she even completed 60 days of sobriety on the Friday before her passing, which made her extremely proud … along with all the work she was doing with her AA meetings — including leading them by herself.

That’s what makes her sudden death — which law enforcement officials are calling an accidental overdose — so much more difficult for her loved ones.

We’re told she lost her uncle to addiction, so she was well aware of the dangers and heartache that come with drugs.

Her mother, Aimiee, tells TMZ she spoke to Kylie the day before her death — she was apparently shopping at Target with a female friend and sounded “cheerful, but a little tired.” Aimee says she thought nothing of it considering her daughter worked up to 70 hours a week to make ends meet.

She says it absolutely crushed her to break the news of Kylie’s death to her sister and brother, who she loved to spoil with fancy meals and beach outings when they’d visit her in Los Angeles.

Aimiee says Kylie was an incredibly kind and down-to-earth person who would do anything for anyone — and would often donate her own clothes, books and toiletries to the homeless. She also had exciting opportunities coming her way … including a recording session with a musician pal.

As we reported, Kylie was found dead in her Hollywood home on June 25 … and investigators found fentanyl and drug paraphernalia at the scene.

She was 28 years old.