(CNSNews.com) - It's been an "intense four weeks," Rush Limbaugh told his radio listeners on Monday - his first day back behind the "golden EIB microphone" since he checked himself into a drug rehab center last month, following news about his prescription painkiller addiction.

Limbaugh said he didn't keep track of the news during his stay at a rehab center because that would have been "counterproductive to what I had to do."

He called the four weeks of rehabilitation "a wonderful process" - the most educational and informative weeks he's ever spent.

"I came to realize some things while I was away -- and at the top of the list is how much I love all of you and how much I appreciate all of you, and how much this and other aspects of my life mean to me."

Limbaugh expressed gratitude for the enormous volume of mail he's received. He said what he went through was "as important as the first grade, and maybe the second grade. It's something...I wish I could have done thirty years ago," he said.

He noted that his two efforts to treat himself through "force of will" did not succeed. He said his recovery requires him to change several aspects of his life, but he assured his listeners that he has not gone liberal on them.

"Many people think that when you go to rehabilitation center for addictions or other things that the people in there turn you into a linguini-spined liberal, and that's not true." He said no one made an effort to change his views.