Jim Carrey -- Left Door Open for Future with Girlfriend Cathriona White

Jim Carrey didn't want to completely sever his relationship with Cathriona White, but never got to explain himself to her before she committed suicide ... TMZ has learned.

Sources close to the couple tell TMZ Carrey only intended to take a short break from White. On September 19th, they had dinner at Nobu in Malibu for her birthday, and appeared very happy.

However, Cathriona says Jim dumped her on September 24th. We're told she wrote about the break up in her suicide letter. Sources tell us friends tried to console White ...telling her Jim still cared for her, but she was too distraught.

As we previously reported ... Cathriona committed suicide using multiple medications prescribed to a Carrey alias.