Play video content

Dennis Rodman's reached a new milestone -- 30 days of sobriety -- but he knows it's a journey ... and he still has a long way to go.

The Worm posted a message for his fans Saturday ... thanking them for the support during his recovery and acknowledging that a lot of people doubted him.

One guy who didn't, though, is his rep Darren Prince ... who says Dennis is "doing what he has to do to take care of himself and become a better healthier person and that’s just so bad ass for this bad boy with a great big heart!"

As we reported ... Rodman entered rehab January 17 -- which he points out was Muhammad Ali's bday -- after getting busted for a DUI in Newport Beach. He checked out a week later, but only to get long-term treatment at the Turning Point center outside L.A.