We spoke with Murray Richman who told us X has already packed on 40 lbs. Murray says he had been nothing but skin and bones before starting treatment in late August at a New England facility.
The program is almost complete, but Murray wants X to stay another 30 days since he's been responding so well ... they're letting him take day trips with a friend to a nearby town.
We broke the story ... a judge signed off on rehab after the rapper said his house arrest for tax evasion wasn't helping him improve. Murray says they'll tackle the court case once DMX has successfully finished treatment. He's also not ruling out a tour in the future.