Jim Carrey's Girlfriend: Suicide Note Shows Despair Over Breakup

Jim Carrey's ex-girlfriend who killed herself wrote in a suicide note she did not want to go on after their breakup, saying, "I'm just not for this world."

TMZ has obtained documents which outline the suicide note written by Cathriona White, who fatally OD'd on multiple prescription meds back in Sept. 2015, shortly after Carrey broke up with her.

White wrote to Jim, "I've spent 3 days now in disbelief that you're not here. I can go on brokenhearted and try to put the pieces back. I could, I just don't have the will this time." She goes on, "I'm sorry you felt I wasn't there for you. I tried to give you my best part."

Sources close to Jim say they were not broken up ... merely taking a break from each other.

White becomes matter of fact, telling Jim, "I don't really know about burial or that sort of thing. You are my family so whatever you choose will be fine."

She adds, "Please forgive me. I'm just not for this world."

According to official docs, it appears White took some of Carrey's meds. Police found a text on her phone from Jim, asking where his painkillers for his back went, noting they were missing from under the sink. We're also told she had been taking painkillers in the weeks leading up to her death ... painkillers that were prescribed to her after a surgical procedure.

We're told White had tried to kill herself with pills in 2012 after her dad died, and she committed suicide on the third anniversary of her dad's death.