Porn star LuLu LoveBottom died by suicide ... TMZ has learned.

According to his death certificate, obtained by TMZ, LoveBottom, whose real name was Lucas Edward Drake, died September 7 at his Los Angeles home.

The document lists the manner of death as suicide, though his specific cause of death remains deferred pending further investigation. No other significant conditions were listed.

As we previously reported ... law enforcement sources told us LoveBottom was found dead at home after an apparent suicide call. His final Instagram post read, "I love you and I'm sorry I was unable to make it to the end. GOODBYE FOREVER. Love, LuLu."

His roommate, Michael, later said LoveBottom died in his room and invited friends and family to a backyard gathering celebrating his life.

The death certificate says LoveBottom was cremated.

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