42-year-old Odom broke up with Sabrina Parr late last year ... just months after the couple was engaged to be married. In light of the split, Lamar says he's made some major changes in his life.

"A year ago yesterday I left my ex-fiance' at the W Hotel in Atlanta without notice. When she realized I was gone back to my home in San Diego she was livid. I received over 250 calls and text messages over the course of last December from her wanting to fix us. We were toxic. Independently and collectively," the former star hooper wrote on social media.

Odom says he "hated being alone" ... and "sought solace in marijuana and a slew of random women, not loving any of them, not really wanting to be with any of them, but it beat being lonely."

Then Lamar says he had an epiphany.

"One day, my soul opened up, light bulb went off and I wanted and needed to change for ME! My team had worked hard to get me a fresh start. I had to honor that 🙏🏽"

Odom knew it was time to make some serious life changes ... and that's exactly what he says he did.

"Today, I am free. Drug free. Pornography addiction free. Marijuana free. Relationship free. I am rebuilding a relationship with myself. With my family. I am focused on my faith. My growth. My brand. I am a legend. I own that. I am a recovering addict. I own that too."

It's a big step for the former NBA All-Star.

Of course, Odom overdosed and nearly died after a night of hard partying at Dennis Hof's brothel in Nevada back in 2015.

Lamar has vowed to live a sober life in the past ... but has sometimes struggled to stay clean.

That is, until now, Lamar says ... and it's clear he appreciates the support.

"I truly love you all for loving me"