Wino inn og út af sjúkrahúsinu

After a weekend at home, Amy Winehouse has returned to the hospital for ongoing treatment.

The 25-year-old singer, whose well-documented substance abuse has triggered a string of medical interventions, spent the past week being treated at the London Clinic. She left the hospital on Friday, but checked back in Monday.

"She had a chest infection [last week] and underwent some tests to make sure nothing else was wrong," a source tells PEOPLE. (Earlier this year, doctors diagnosed the Grammy-award-winning chanteuse with scarring of the lungs.)

Is Winehouse finally committed to getting healthy?

"She has been told to give up smoking and was initially struggling with that – she was covered in nicotine patches at one point," says the source. "But she is making an effort."

The notoriously skinny singer was photographed looking somewhat fuller in the face last weekend – a healthier look that won praise from two British tabloids.

Despite her health woes, Winehouse has been recording tracks in her home studio for an upcoming album, her London-based rep, Chris Goodman, tells PEOPLE.

The 25-year-old has even been learning to play the drums, he adds. "We'll have to see how that plays out on the next album."

Source: People