Troubled pop star Robbie Williams is suffering a "living hell" because of his drug addictions - according to his mother JAN. The British singer is being treated for addictions to caffeine and prescribed medication in Arizona's The Meadows Clinic. The latest problems come after years of battling alcohol and drug addictions - and 52-year-old Jan - herself a drugs counsellor - claims Robbie is desperately unhappy. Admitting she missed the signs of his troubles in advance, Jan says, "There was one time when he came home in the middle of all his drink and drugs problems - and he lay down with his head on my lap and he was sobbing. "It is very, very hard when your child has problems, alcohol and drugs just don't affect the person who takes them. As a mother it was mind-blowing. Even though I was relatively skilled it just went under the net and I never saw it. "Some of it has been a living hell." Jan is currently in Arizona, visiting Robbie, who is half-way through an eight week stay at The Meadows.