What Causes Bad Breath And White Lines On Tonsils?

Hi- I just noticed my 4 year old son has terrible breath. While brushing his teeth I noticed tiny white lines running all along his back throat and tonsils. The area seemed swollen. He has no fever, signs of cold, etc. When ask if his throat hurt he told me only when he swallow. Any idea what this might be. He has never had strep throat.