Can jaundice return in baby and be harmful?

When my son was born he had mild jaundice and after a few weeks it went away on its own, however now at 6 weeks I have notciced his eyes beginning to yellow again, also to my concern he has been sleeping more and eating less and seems to be a bit more fussy although he isn't awake for very long to fuss much, should I be concerned or will the jaundice go away again and he is just growing..??